Something I Never Expected

I never thought I'd end up with someone else while still married to my ex. We had been separated for a few months and things were amicable, but then out of the blue, I met this person at a party. It wasn't like me to be so impulsive, but something about them just clicked. Before I knew it, we ended up together that night. I feel terrible because while they mean nothing to me now, it still doesn't excuse what happened between us.