"Johnny..." Daniel started, wanting to pick his words carefully. "You know you don't have to explain or justify sleeping with anyone, right? We broke up. You don't have to feel guilty or apologise for sleeping with other people during that time." Even if technically they had still been married so had both actually committed adultery in the eyes of the law. Morally speaking though, they had both been free to see whoever they wanted.
"Part of me is selfishly glad you didn't find someone long-term though, otherwise we wouldn't be here now."