Butterfly effect.

I think that's exactly what it means to "live in the past," especially when it happens too often. But when special, life-changing moments stay in your mind for a long time, can that really be called "living in the past"?

You probably misunderstood me, or I didn't express my thought correctly.
I meant that there are many chains of events in our lives, and I can't really single out one that is truly significant, probably because I haven't lived long enough yet.
And I rarely think about the past, except when I come across an old photograph or meet an old friend.