Advice, Please?

[sara1998]

OK, this is a little personal (for me at least) but I want to ask people who are not close to the situation for an opinion.

At one time, about 4 years ago, my best friend of 20 years was engaged to a wonderful guy. She cheated on him, so he left. (I don't blame him) Since, she has been involved with a few others and is now engaged again. She has told me that cheating on him was the worst mistake she's made in her life, and it hurts to talk about him. OK. A few weeks ago, he called me just to BS, see how I was doing, and wanted me to go out and have a few to catch up. So, we did, this past weekend. We went to the boat, lost money, and had a blast. We're both interested in eachother, but I feel unbelieveably guilty. What do I do? What would you do??? The last thing I want to do is scar or even ruin a friendship of over 20 years because of this.