Conflicted After a Party Night

I went to a party last night and ended up with someone I barely know. We were both pretty drunk, and things got heated in the back of his car. It's not that I regret it, but it felt so wrong given where my fiancé is right now. He’s deployed overseas on duty, and here I am acting like this. How do other people handle these situations? Is it normal to feel such guilt even though we were both consenting adults?