By Tyler Cowen, Money Magazine contributing writer
(Money Magazine) -- One reason behavioral economics has become such a hot field is that it has scads of practical applications. It can help you fire someone, choose a great restaurant, or get other people to do the dishes.
But at your child's graduation from college or grad school, more important life lessons are in order. Three of them are based on the same insight: One of the hardest and most important things to do in life is to behave rationally -- or, put another way, to know your limits.
Your career: Heed your enemies.
In your business dealings, the people with whom you butt heads are often those who have the most insight into you.
If someone thoroughly annoys you, chances are he has a good sense of your faults (maybe that's why you're annoyed!) or holds a point of view you don't often hear. Listen closely. Understanding the value of what your adversaries have to say will help you improve, giving you a big leg up.
Your investments: Buy and hold.
People always like to think that they can beat the stock market. They're almost always deluded. No matter where you think the market may be headed, stick to a buy-and-hold strategy. You'll make more money in the long run, in part because you'll minimize your taxes and trading fees.
Your love life: Understand the odds.
When you have an argument with your future spouse, about half the time you're in the wrong. Grasping that hard-to-accept fact is one of the best ways to save yourself from a costly divorce.