Speaking of it...that "let me drown in self pitty while I get depressed in my nostalgia" song of "The Beatles- Yesterday" comes to mind. No offence dear Beatles, but that is one lame song!
Yesterday does no longer exist, so to spend your todays and tomorrows thinking about that...really?
Even more, people let themselves be defined by their past. And that is sooooo inacuratte! Because it's like Heraclit said: "No man ever steps in the same river twice, for it's not the same river and he's not the same man." I used to be tormented of things that happened in the past, "omg, why did I do that?", "If only...", "if I could turn back time...I would act so differently" until I realised that I'm wasting my present remaking my past.
I just remembered a funny/wise/true thing one of my childhood friends use to say: "Ce-a fost a fost si nu mai este!"
So, fuck yesterday! Welcome today!