The striver's curse is that the people on the lower branch, the people who tend to get unhappier as they age, tend to be the ones who experienced a lot more success earlier in their lives. And it kind of makes sense—what goes up must come down. If you don’t do anything with your life, you won’t know when it’s over. But if you do a lot with your life and the party ends, you’re going to notice the difference. That contrast is really hard to take.

Early in life, we have a lot of what psychologists call “fluid intelligence.” That increases through your 20s and 30s—it increases faster if you work harder on it—but it decreases in your 40s and 50s. Fluid intelligence is your ability to work hard with focus and solve problems, your analytic capacity, what makes you a superstar—the hot lawyer, the good surgeon, maybe the incredibly inventive and intelligent electrician. In almost every job, fluid intelligence early on in your life makes you good at what you do, but it decreases as you age.

Crystallized Intelligence increases through your 40s and 50s. It stays high through your 60s and 70s, and even beyond. Crystallized intelligence is not all about working hard and focusing—it’s about wisdom and passing on knowledge. You get wiser as you get older, which means you know a lot, and you know how to use the information. It also means you’re a much better teacher—the best teachers are older people. So early on, you have fluid intelligence, and later on, you have crystallized intelligence. The trick is to go from fluid to crystallized, to go from innovator to instructor.

One of the things that all happy older people have in common is that they don’t just know how to add things to their lives; they also know how to subtract things from their lives. Early on, life is like a canvas that you’re filling up with paint—creatively, with energy, with enthusiasm, more brush strokes, more pain! And it’s all up to you—what you paint is limited only by your imagination. But after a certain point, that canvas gets pretty full.

To be happy as you get older, remember: don’t just add, subtract.

One of the most interesting things in the neuroscience and social science of happiness is that happiness is based on love. Love is the nuclear fuel of happiness, and if you don’t have a lot of love in your life, you can’t get happier as you get older.

And that means you need to work on the love in your life. You need to cultivate your relationships, whether they’re your friendships, family relationships, or marriage. You’ve got to see them get better as you get older so that you can get happier as you get older.

Maybe you’re a striver and successful, but you’re kind of lonely in your relationships. Well, successful people usually have a lot of people around them. They have a lot of “deal” friends. How many real friends do you have? Go from deal to real, and watch yourself get happier.