How do I simmer down when I can't have sex?

Sometimes when my girlfriend isn't in the mood I get really upset and bummed out, I try not to express it but sometimes I just can't help myself, I find it hard to go to sleep because the whole thing makes me feel a little undesirable, but i'm more mad at myself for acting like a baby by griping about it and upsetting her, which I realize after the fact is a huge turn off, so how do relax? because I also get a bit squirmy when this happens too. I love her to death and have not intention of breaking up with or cheating on her. Also going to the bathroom and jackin it doesn't help anymore.