In The Futile Pursuit of Happiness, JON GERTNER writes,

we overestimate the intensity and the duration of our emotional reactions -- our ''affect'' -- to future events. In other words, we might believe that a new BMW will make life perfect. But it will almost certainly be less exciting than we anticipated; nor will it excite us for as long as predicted....[T]est participants through the years have consistently made just these sorts of errors both in the laboratory and in real-life situations....On average, bad events proved less intense and more transient than test participants predicted. Good events proved less intense and briefer as well.