Most people think the phrase "get over it" means to "forget
about it." If I were to forget about something in life then I would bash my head wild open with a big glass of bottle wine to erase my memory so that way I can't look back.
When we say "get over it" we are saying "Don't let the past ruin your life" or "Stop living in the past and stick with the current event."
Friend: My ancestors were the victims of Halocaust
Me: That was the past, get over it.
Friend: But I don't wanna forget about it.
Me: No, I meant don't let the past screw up your life.