That One Moment...

I met this guy through work, we've got something solid going on the side. Everything's fine until last night when... well, there was that moment. We were in his car, alone for a few minutes while running an errand, and it happened. I'm not sure what exactly triggered it, maybe just being so close to him after hours of customer service smiling, but suddenly I found myself initiating something intimate. It felt wrong as soon as it started, yet my body didn't want to stop.... How do you keep that sort of thing from happening when everything else between us is good? Am I the only one who feels this way?