I don't know what to do. I work in a smallish team and we all get on really well. I was at university with my immediate boss about 10 years ago, we knew each other, but not all that well and I hadn't seen him until I started this job last year. I have just come out of a 5 year relationship and he has been single for the last year or so since his engagement broke up. We were working late to meet a dealine last night and were joking around, I have no idea what came over us but we were both being a little flirty and we ended up kissing. I went back to his apartment and we ended up in bed together. I never do this! Now I'm really worried about seeing him at work on Monday. Should I just act like it never happened or try and speak with him about it? I feel like a total idiot, and can't believe I did this.