You gotta be strong. Old memories are in the past, past as in over, it's not happening now, so you don't gotta worry about it anymore. That's how I feel about stupid stuff or sad things that happened to me in the past. Feeling better?
NP. Idea!!! If you ever feel sad, watch an MLP episode. Trust me it never fails as a cheer up mechanism. For me an episode like that is MMMystery, so much references, cake, Pinkie, and still unexpected ponies who ate the cake.