The Night I Cheated With My Best Friend's Partner

I had been married for seven years when my world changed overnight. My best friend, Mike (no last name), started hanging out with me more and his girlfriend wasn't around much... We started talking a lot over drinks, laughing at inside jokes... One night we were texting late and I couldn’t stop thinking about him... He came to visit on a whim and before I knew it, I was kissing him... We spent the night together... I feel like such an asshole but it felt so right in the moment. What should I do now?