Do you ever want to do something, completely in the moment, and then you don't, cause you're too shy, or awkward or scared. But then you think about it constantly for the next few days, finally resolving to do it the next time the opportunity arises. But then it's too late, and you will never be in the same situation again.

And then you can't get it out of your head? It plays over and over for weeks, and then it sort of goes away. But then, later, months later, years, it pops up again. And you're full of regret.