How do I clear my conscience?

So this incident happened a few weeks ago and it's been killing me ever since it happened. So basically I was at my friends house party. I was just standing around drinking with a few friends. A girl right in front of me turned around and saw me and my friends behind her. About a minute later she started throwing it back at me. So I took it as a sign she wanted to grind on me, so I moved up on her and grabbed her butt. She moved away and told me to back off. I apologized profusely, and moved away cause I was super embarrassed. I keep thinking to myself that I'm a terrible person for what I did and have been feeling super guilty ever since. Maybe I don't deserve to, but how could I go about clearing my conscience about what happened?
How do I clear my conscience?
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