Recently I realized that I love one of my best friends.
I've known him for years, and for a long time thought of him as just a friend, but a few months ago I finally realized that I'd really liked him for a long time, I just hadn't admitted it to myself. Since my feelings weren't incredibly strong, however, it was pretty easy for me to ignore them and not dote too much on them.
However, recently, after a long night of talking seriously with him and some other friends about our pasts and things like that, I realized that I actually loved him. The problem lies, however, in that he has a serious girlfriend who I happen to be friends with as well. Although I won't deny that I really want to be with him, because they're really happy together and I don't want to hurt his girlfriend, I'm not going to say anything or hint that I have feelings for him. I'd rather not say anything and be friends than mention it and have them both feel weirdly towards me.
But, the more time I spend around him, the more strongly my feelings become. Is there any way to lessen my feelings for him? Spending less time around him isn't an option because I only see him once a week, and it's at a gathering between all our friends that we've been doing for over a year. I don't really know anything else to do but keep busy with things so I can't really dwell on things, but does anyone else have any other ideas?

Thanks!