Along those lines..
for a psychological trauma of the past I tell myself: the whole universe, all of existence, did a wonderful job in burying it in the past, only 'me' is able to reproduce it's echo's into the now, to bother about.
Things get different if one lost for example a leg in a trauma, it's harder to put that in perspective. But is it? I must have been 16 or so witnessing 4 joyfully playing dogs in a field, oh what a fun they had. Then I noticed one of them had only 3 legs. That 3 legged dog seemed to have most fun of all. I thought "shouldn't that dog not be discontent?" It did not! That was a lesson I took dearly.
However the most difficult things I find to leave in the past, not letting those affecting my todays, are guild feelings.