How many people have chosen to use or buy something isn't a perfect measure of its value, but it's a pretty good indicator. And by this measure, Yale psychology course Psych 157: Psychology and the Good Life must be incredibly valuable. 

A full quarter of the Ivy League school's students enrolled in the course when it was offered, making it the university's most popular class ever. When learning platform Coursera started offering it for free online, a whopping 255,000 people signed up. Many raved it changed their lives. 

Which means it's almost certainly worth taking. But what if you're short on time and can't devote weeks on end to a course, however excellent? Then Laurie Santos, the professor who teaches the course, has a shortcut for you. 

Last week at the Aspen Ideas Festival, the psychologist presented the "shortest possible crash-course version of the class," reports The Atlantic's Joe Pinsker. Here it is boiled down to just 593 words. 

People get used to everything. 

Studies show that even when people experience an extreme trauma, like an injury that leaves them in a wheelchair, they generally bounce back to their pre-event levels of happiness fairly quickly. The same is true of lottery winners. After not too long, becoming a millionaire probably won't make you any happier

Both these facts illustrate the same basic truth: people can and do get used to everything. That's good for weathering difficulties, but it's lousy for our ability to estimate how positive gains will impact our happiness. Chances are great that whatever you think will make you happy - be it a bigger paycheck, a larger house, or a fancy degree - will actually become routine for you once you get it. 

What should we do with this lesson, according to Santos? She offered two takeaways: 

  • Buy experiences, not things. This has been said so often it borders on cliche, but it's popular because it's the research-backed truth. A vacation is too short to get used to and will provide you with memories to enjoy for the rest of your life. A new car just gets old. 

  • Practice gratitude. Again, nothing groundbreaking here, but Santos insists a basic gratitude practice, where you set aside a little time each day to think about what you're thankful for, will really move the needle on your happiness. 

Comparisons kill happiness. 

Maybe you read about the study showing bronze medal winners appear way happier than silver medalists, despite finishing behind them. The results teach us something important not just about Olympic athletes but about ourselves too. We tend to measure ourselves via negative comparisons rather than in absolute terms (i.e. "I almost won gold" versus "I am a stellar athlete achieving a lifelong dream.") This makes us unhappy. 

"Our mind just happens to [pick] whatever reference point seems to be salient at the time, whatever reference point we happen to notice, and it tends to particularly [pick] reference points [involving people] who are doing better than us, which kind of sucks," was Santos' blunt summary of this tendency.

How do you get around it? Again, Santos offers a quick prescription:  

  • Deprive yourself. Simply taking away something you've come to enjoy for a day or a week will give you a fresh appreciation of what you already have. "A summer night or two without air conditioning might make the rest of the season much more enjoyable," is Pinsker's example. And if you can't actually deprive yourself, force yourself to really think about life would be like without some of the pleasures you currently enjoy.