I find that memory is strange, not 'bad' or 'good'. In general it will remember stuff for a while unless you concentrate hard. Bad stuff might get 'forgotten' a little quicker than good stuff, or the reverse.
Stuff that you really want to remember sometimes gets lost for no apparent reason.
I used to be able to remember just about everything that I wanted but lately (now almost 45) that is getting noticeably harder.
Traumatic stuff is in a class of its own. Some people will never be able to get away from it, others have it suppressed to the point where it might as well not have happened.