Girlfriend issue, opinions?

We were having an argument about her never being on time when I made a comment that she didn't like too much. She tried to get up and walk away/run away, and I grabbed her pants leg to try and stop her. She started to fight me and scream and scratched my upper forearm and I bled a little. In the resistance she hit me in the face-not hard enough to hurt or bruise but it hurt me more emotionally. She cried and cried and cried afterwards apologizing to me but I really don't know what to feel. I never hit a girl before and never will, so I never retaliated for her hitting me. But I did lose my cool and yell back at her. I feel confused and sick about the whole thing. I don't really know what to feel, or how to even begin to get over it. What are your opinions? Should I forgive and forget? Is it normal to feel so emotionally let down and dissapointed? How do you get over that?