I know a lot of other people with borderline and other dissociative issues struggle with this too. 

I feel like my memory is sort of selective sometimes. For instance I sometimes "forget" bad events. Although I actually don't. It's just that people in general tend to remember highly emotionally arousing memories much better and clear than the mundane ones. Like if someone hit you or if you freaked out and started destroying things, you would probably remember those particular instances more distinctive and clearly than what shirt you wore for a trip. But to me, both are just another memory. Both are just things that happened. Like "Oh yeah, I DID do that! Hmmm..."(I mean this were some pretty bad example with the shirt stuff, I just couldn't think of anything better.)

  
Also depending on what mood I'm in I can remember a specific person or sequence of events as completely different. Sometimes I remember a certain period as rays and sundshine while at other times I think of that same time period as excruciating and unbearable. It's just really random sometimes. Idk