When you have 21 minutes to speak, two million years seems like a really long time. But evolutionarily, two million years is nothing. And yet, in that two million years, the human brain has nearly tripled in mass, and something remarkable has developed: a prefrontal cortex that allows us to simulate experiences before we have them.

Here's a puzzle that has driven my research. It turns out that lottery winners and paraplegics report similar happiness levels a year after their life-changing event. Both groups end up at about the same level of happiness, and this is the most surprising finding in my field. A year after winning millions, a year after losing the use of their legs — roughly the same happiness.

Why? As a matter of fact, we're remarkably good at this — we call it the psychological immune system. It's a system of largely unconscious cognitive processes that help us change our views of the world, so that we can feel better about the worlds in which we find ourselves. We come up with reasons to be happy with whatever outcome we get. "At least I learned something." "At least I met that person." "At least it wasn't worse."

Now, this doesn't make sense to most people. It doesn't make sense that we'd be happier with less choice, but the data shows we are. It doesn't make sense that people with fewer options sometimes report more satisfaction than people with many options. But that's what we find, again and again.

Money brings happiness up to a point. On the other hand, beyond that threshold, gains are minimal. Once your basic needs are met, additional income has a smaller and smaller effect on how you feel day-to-day. We're much better at manufacturing happiness than we think. The secret is that we don't need to travel to Hawaii or win the lottery. Natural and synthetic happiness are both real. And understanding that can change how we make decisions, how we set goals, and how we live.