It's humans' nature, I guess.

得不到的，永远是最美的。但，得到了后，会珍惜吗？
Humans are never satisfied.
Well, that's the main cause of every war during the ancient time, isn't?
To conquer other country, get more land and increase their army's strength.
We only think of getting more and more and more.
Knowing that there's no limit, we won't control ourselves.

When you're single, you see happy couples and when you're in a relationship, you see happy singles... we're never satisfied. - Bob Marley

When you're longing for something,
you'll use thousands of excuses to get yourself there.
But once you've got it,
you realize that it's not that perfect.
And eventually,
you'll aim another 'best' thing.