It’s hard to be the one to speak up when your partner is having fun. I, unfortunately, took a very long time to accept (I knew it in concept but didn’t feel it) that my partner has less fun if I’m not having fun. It’s not really about the sex - if it was just about having sex then bad sex would be enough. It’s about engaging in a fun sexual environment with my partner. So if I’m not having fun, don’t feel it, then my husband enjoys his experience less as well. And why sacrifice??? Don’t throw yourself in the grenade unnecessarily. You don’t HAVE to have sex with anyone if you don’t want to. Talk to your partner and figure out a plan for when this happens again (as long as you’re swingers, there will be times where it works for one but not both), but forgive yourself for being human and not following the plan when hope clouds your judgement. It’s ok to make mistakes - it doesn’t make you stupid, it makes you a person.