“I was drunk”
While drinking can certainly cloud one’s judgment and plenty of bad decisions can be made after sipping more than your fair share of cocktails. However, that is still no excuse for cheating.
Millions of drunk people manage not to sleep with any willing body. You’d be astounded at how many folks get drunk and don’t cheat because drinking is not always followed by sex. And in the instances that it does many people in relationships chose to sleep with their significant others!