Why do most women never learn to let go?

Easy answer: Yes. It is difficult for girls to let things go...anything you do will automatically be stored for a later time when you have an argument. Very few women have the ability to let emotional moments go. Why? Good question but no really good answer. That is just the way it is. Sorry but it is true.

Learn to read girls. It must have affected her a lot if she keeps bringing it up in every argument because I would if it really hurt me.

Honestly if we girls hang on to things that happened in the past it is because it really got to us. You may not see it as a huge deal but we think about it a lot more than you know. You have to think about the sensitivity factor here as well. Girls are more sensitive than guys and minor things can tick us off. Guys just need to learn how to read a girl.

Maybe it made her really question you/herself/her life view or something? I hold on to stuff, but usually only when it really makes me wonder if he's really who he seems to be. Or if it shows some deep philosophical disagreement. Or really confuses me - if I don't understand the position or how the person can hold that position.

And sometimes, it's just really stupid sh*t that hangs around in the back of your head and you just can't get rid of it. Those, I typically try to hide better - just because my subconscious is crazy doesn't mean everyone else needs to know... :P

In a sense it's a women thing, our feelings will and always be deeply into someone we care about, simply because guys don't notice things that girls may seem to notice like ALL THE LITTLE THINGS... YOU KNOW???

Yeah I agree with stanley. Some people just don't have the ability or mindset to let things go. It's a choice to hold onto things, not something that just happens. Maybe she feels stronger holding onto something she can use against you, or maybe it just plain really really hurt her and it's something that seems insignificant to you, but huge to her. Being in a relationship with an unforgiving person is one of the hardest things you could ever do. Wish I could help more, so good luck with it all!

It depends on the thing. If you had an indiscretion with another girl, then I would expect that to hang around. But if it's a question of a comment made or standing her up or calling her mom fat last year, then it should be laid to rest. One of the quickest ways to screw up a relationship is to not let go of past issues, to bring them up every time there's a disagreement. If the Supreme Court can limit themselves to deciding the issue at hand based on the narrowest boundaries (i.e. the specifics of this law and its precedent), then surely the rest of us can as well.