How does one deal with trust and worrying?
a) Say my girlfriend has done something stupid that hurt me pretty bad, and I ended up finding out myself rather than by her telling me. She apologizes profusely for it, is honestly sorry, and realizes what she did and how it's messed up the relationship. I know she won't do it again, and I know for a fact that she does truly care about only me and has no feelings for anybody else, but the fact is that it still hurts and I just don't know how to get over it - I can't she how she even did it in the first place (I think this is partially due to the fact that I've never done anything along those lines - never really even considered it - and so the idea of it is just completely strange and unnatural).
b) As for worrying, is there anyway to stop worrying so much when she goes out with friends or things like that? I honestly don't know if it's just me caring for her that much (I honestly feel that I'm in love or close to it with her, though I haven't said it yet and don't plan to until I'm sure) or if I'm just paranoid - most likely a bit of both. I don't know her friends personally, but I do know that some of them are people that I honestly don't like her hanging out with.
Blah.
First of all...
I know she won't do it again,
That's a lie, or you wouldn't really need to worry about her actions regardless of who she's with.
Secondly, I've had a girl cheat on me and I trusted her not to do it again. She did it again. Since that time, it's never happened with another girlfriend, but I've watched my friends around me and, speaking from experience and what I've seen -
if she didn't tell you herself, it will, in all probability, happen again. No one deserves that, and if there's any doubt whatsoever in your mind or heart, get out.
Thirdly, if it was something sexual that she did with someone else and you weren't willing to give it to her, then there's two things to consider here. You should either rethink whether or not you want to engage that kind of relationship with her (that's probably why it happened, if this is the case), and if you decide you don't, the two of you should see other people anyway. If you can't or won't keep a girl sexually satisfied and she is the sort of individual who craves/desires that kind of gratification, she will find it. I learned this the hard way before I thought I was ready for sex. I will say this - if the reason you don't want to engage that sort of relationship isn't spiritual or something along those lines (IE, you just feel like waiting) and you care about this girl at all, I'd suggest starting some sexual interaction. If you're just waiting to be waiting, you're accomplishing nothing and, as long as you're safe and committed, a sexual relationship is immensely rewarding, and the rewards only become greater as the two of you become more experienced and more in tune with one another. However, if this defies your moral compass, you should probably see other people to begin with, since it obviously doesn't defy hers...
Finally, no one deserves that kind of treatment, and you have every right to end the relationship. If you do, though, make it a cool, clean cut. Don't drag things out and delay and piddle and let her talk you into "one more chance" or anything like that. If you make up your mind, don't let her change it. She shouldn't have cheated, and she should realize that.
As for her friends, if you don't like who she's with, tell her. If she's with the boy this happened with, you have every right to say you don't want her with him. As for other friends, you need reasons to ask her not to hang out with them. But you need no justification to simply say you don't
like that crowd.