My Mom would tell me "You shouldn't cry over spilt milk"
and a bunch of the ones already mentioned.
My sister would tell me (A perfectionist) "It'll never be noticed on a galloping horse", I still haven't figured that one out.
My other sister had one "For crying in the bucket" used when things weren't going right.
A modern one is the definition of studipity "Doing the same thing over and over and expecting different results"
Don't worry, be happy.
I love reading all of the sayings, some bring back a lot of memories.