When you enter a romantic relationship, or get married, or have a kid, you are jumping onto the so-called "hedonic treadmill." An initial period of bliss will subside and you will eventually return to a relatively stable level of happiness. Happiness is a treadmill in the sense that you need to keep working at it.
In today's lesson, Sonja Lyubomirsky dispatches some of the most common myths about happiness, namely that certain life-changing events will lead us directly to happiness, or conversely, to a state of being unhappy. As Lyubomirsky points out, this reductive understanding of happiness represents a false promise. After all, you can be unhappily married or happily divorced. It all depends on how you manage expectations and train your brain to take the best advantage of your circumstances.