Žižek gives the example of a married man who has a cold relationship with his wife and a mistress. Every day, he dreams about the same thing: "If only my wife would leave, I could finally start a real life with my mistress." The moment his wife leaves, he discovers that he doesn't want the mistress. In reality, he only wanted to want her. He liked the idea of her. His marriage was just an obstacle needed to keep his desire alive.

I've been thinking about this a lot, and I see this pattern everywhere.

I see this in immigrants who spend their lives fantasizing about going back to their country. The moment they get back, they cannot spend two weeks there.

I see this in men and women who spend their adult years looking for the perfect partner. The moment they find one, they can't handle it.

I see this in entrepreneurs who spend their whole lives chasing an exit. The moment they get hundreds of millions, they get a "post-exit identity crisis." 

Schopenhauer said: "Life swings like a pendulum backward and forward between pain and boredom." 

Once you get what you want, you don't arrive at peace. You arrive at... nothing. The desire itself was what gave things meaning.

Rationally, this might seem paradoxical.

But who said that we are rational in the first place?

I wrote about this more here if you're interested including what psychology says about why we keep falling into this loop (impact bias, hedonic adaptation), and whether there's any way out of it.

As humans, we don't want what we think we desire. We want to want it.