Nostalgic

right now I'm just thinking about my past, trying to get some lessons from my mistakes..well if there any mistakes I've done, few of them i totally regretted and if i have regrets i think its about thinking of my past. But i keep asking myself "why i keep being nostalgic??" is there something in the past i cannot leave behind?? is there any??

some says try to forget it by doing something..but me?? the way i am right now?? I'm helpless:(