A book by Professor Carl Pillemer of Cornell University, a world-renowned sociologist and authority in the field of human ecology.
This book is a collection of objective and professional advice on love, marriage, and relationships from over 700 elderly couples who have been married for a long period of time, from 30 to 70 years.

In particular, the elderly American couple chosen by Professor Karl Pillemer as a research sample are a generation that has endured hardships in life that are difficult for modern youth to imagine, going through world wars and the Great Depression. They are experts who can impart the secrets of a century-long marriage that will not be broken by any external environment.
There is probably no advice as specific and practical as that given by people who have actually lived together for a long time.

Karl Pillemer compiled hundreds of hours of interviews and thousands of pages of records, distilling the wisdom of life, love, and people from the wisest minds of our time into 30 practical tips that couples can immediately apply.
How to choose the right partner for you, how to communicate between couples that require technique because they are the closest, how to wisely overcome the difficulties of married life that can be a series of stresses such as making a living, raising children, and in-laws, and the secret to maintaining the passion and sexual pleasure of the first heart throughout life are told through the vivid 'voices' of life's sages.

"How do I know if she's the one I'm looking for? Isn't that a question of 'can I trust my intuition?' To know that, I have to listen to my inner voice.
Even if it's a little awkward, you have to try to listen somehow.
The answer is there.
Your own intuition, that is.
A rational person would look through the book, make a list of things to do and things not to do, and then check whether they have been properly implemented.
But ultimately, without this intuitive feeling, you can't go any further.
Falling in love.
You shouldn't just listen to it and try to understand its meaning with your head.
I understand it on a deep inner level, from intuition.
It's a kind of innate ability.
Falling in love means not knowing exactly what to do, but being guided by intuition to do it because it's the right thing to do.
“I don’t know for sure, but I’ll get a feel for it once I see it.”
--- p.52

“Find someone with similar values.
You have to spend time with someone and see their true colors.
I think we need to do some background research.
Not like the police do.
I'm telling you to find out what kind of person they are and what kind of background they have.
When choosing a spouse, don't look for trivial things like appearance, but look for something deeper and more important.
The importance of faith, values, and parenting… … .
“These are the things that make for a truly enriching marriage.”
--- p.67

“To avoid serious conflict, you must first and foremost get in sync with the rhythm.
We must become one with each other.
There are many couples around me who live well even though they have different interests.
But I think common values ​​and principles are absolutely necessary.
Being in the same rhythm means having the same outlook on life and long-term goals.
“Even if the paths are different, we must have a common goal and plan.”
--- p.73

"What's the point of marriage if you don't have open, enjoyable conversations with your spouse? It's important to always be able to communicate with each other.
If you lose the conversation, you lose the marriage.
Isn't it true that two people living together are supposed to talk about family history, worldly affairs, and everything in between? There's a lot to talk about, isn't there? Politics, health, anything.
Always keep the door of conversation open so that the conversation can continue.
What's better than conversation?
“It’s hard for a couple to get along without talking.”
--- p.114

“Couples should respect each other.
This means that you don't say anything to your spouse that you wouldn't say to anyone else.
Just because you're a spouse or partner doesn't mean you don't have to care about their feelings as much as you do about others.
It means that you should be polite and treat others kindly.
Even when you're angry, you should show your spouse the same courtesy as you would to a friend.
It's such a simple thing, yet so many couples fail to do it.
“They completely forget that fact and act and speak recklessly without any consideration for the other person.”
--- p.132

“Trust is the thread that connects everything.
That's the most important thing.
Because if you have that, you can overcome many other things.
If you're insecure about your relationship and don't trust your partner's honesty, you'll feel anxious when he meets other friends on his own and worry when he pursues his own interests without you.
You can't be around and monitor someone 24/7 to keep the relationship fresh and fun.
If you're honest, that won't happen.
“Because I believe that you are someone I can feel safe with even if we are not together all day.”
--- p.161

"You're stuck between us, no way! I had this wonderful woman by my side, and we were happy from the moment we met.
My mother was against it and it hurt my heart a lot, but that didn't change anything between us.
My theory is that if a spouse takes the parents' side, the conflict between mother-in-law and daughter-in-law will never be resolved.
If a couple is not completely committed to each other, the relationship is likely to be difficult.
You must stand on your spouse's side.
Whether the spouse did well or did wrong, the couple is one.
“We must stick together in any situation.”
--- p.193

“He gave me such good advice.
He said, 'There's no need to make a hasty decision.
And it's even worse when you're so angry, upset, and desperate right now.
That's not something you need to decide on right now, is it? Think about it over the next year or so.
And if you really want to break up, then do whatever you want.' But something changed dramatically in that year! Things had completely changed! After I talked things out with my husband, he drank significantly less.
Since then, I've given the same advice to others.
There's no need to make a hasty decision.
Wait about a year.
Understanding other people's minds isn't something that can be accomplished overnight.
It takes at least a year for both of you to really think deeply about what you really want in life.
“Each of you should back your car into a corner and think deeply.”
--- pp.226-227

“It’s like we like each other as friends.
When you're young and deeply in love with each other, it's hard to take a step back and ask yourself this question.
"Are you sure you like not just these hands and body, but also what's behind them?" That's what will make your relationship grow and deepen over time, without it wearing out.
Well, the sexual aspect is also getting deeper.
But as time goes by, that importance will diminish and camaraderie will take up more of it.
Because there are so many problems that we have to overcome together: children, adversity, parents, etc.
Also, as your interests or lifestyle change, your thoughts about them are bound to change as well.
But the sense of companionship between a couple is the unshakable foundation of a solid relationship.
So, you have to really like each other and enjoy being together.
“That requires friendship.”
--- p.251

“I went to see the opera.
I'm talking about opera! I don't like that kind of thing.
But even though my wife hates baseball, she goes to the baseball stadium with me.
So we decided to split it in half.
I try to do what my wife likes, and my wife tries to do what I like.
But I really didn't want to go to the opera.
I wonder if the man is some kind of opera.
But I held on tight and went.
And guess what? It was worth seeing.
It was the same with ballet.
Oh my gosh, ballet, that was horrible.
I went anyway.
I like it better now.
My wife doesn't know anything about baseball.
Still, it's fun to go there and cheer together with people.
Isn't that the spirit of compromise? That's the secret to a fulfilling and enjoyable married life."
--- pp.256-257

“Don’t go to bed angry at each other.
When you're young, that doesn't work very well.
Especially on days when we fight with each other.
But before you go to bed, make sure you say this.
"I love you." Then, the next morning, you'll be much more comfortable with each other.
Don't put off today's work until tomorrow.
Every night I clean everything out before going to bed.
“Don’t leave it feeling stuffy, just clean it all out.”
--- p.275

“Try traveling! Being exposed to different environments will change your perspective on life.
If you just stay at home, your daily life becomes boring and dull.
I just live my life as I always have, without thinking about anything.
If I leave home for a few days, my lost passion will be revived.
I can definitely feel the difference.
You will be able to feel the joy of being together again.
My husband and I had a wonderful time traveling abroad for a year in our late 50s.
It was really fun learning a foreign language together.
“I mean, constantly experiencing new things.”
--- p.287

“We must respect each other.
Respect is valuing another person's character and contribution to the world.
It is fundamental to accept others as they are.
I've seen many people who are unhappy because other people don't do things the way they want.
But respect is valuing not only the personality of another person, but also their thoughts and beliefs that are different from your own.
Respect is not about control, it's about freedom.
“Recognizing each person’s rights.”
--- p.304

“From now on, I must forget about myself.
Marriage is compromise and teamwork.
You should do this when you speak too.
'We have a problem.
'Shall we talk?' Learning to work together and collaborate as a team is the most important thing you can do in marriage.
But these days it's really hard to do that.
Because the individual ‘I’ is much more important than ‘we’.
This is what my husband and I did, and this is what I recommend to young couples: work as a team.
“We will live with the same goals, values, and desires, and we will be willing to compromise when we have differences of opinion.”
--- p.310

“Marriage is when two people live together and become one.
Two souls become one body.
The most important thing when deciding to get married is commitment.
You must be confident that you will spend your entire life with only this person.
Sometimes I see people who think they can get a divorce at any time if they decide this marriage isn't going to work out, but you shouldn't treat marriage as a contract that can be cancelled at any time.
If that's what you're thinking, then don't even start."
--- p.350

“After being married for about 30 years, I realized that people grow through marriage.
The breadth and depth of that growth is truly astonishing.
Looking back, I think that the very small changes that have accumulated have made me who I am today, completely different from the past.
Now I can say it with confidence.
I finally found my true self.
Some people might ask this.
'Was there a major turning point in your married life?' Absolutely not.
Living with your spouse, loving each other, day by day, you gradually take shape.
Think about plants growing.
The sight of living things growing.
“It grows little by little every day and endures wind and rain to finally take on its true form.”

--- p.359