In 2004, I became friends with a co-worker, named Tony. It was exciting to find a friend with whom I had so much in common. We would have lunch together regularly, go out for drinks or dinner after work some nights, and program computer code together -- the usual things friends do.
In late 2008, I noticed Tony didn't want to have lunch anymore; all invitations for social activities were turned down. It actually took me a while to really understand he was actively avoiding me. I finally spoke with a mutual friend who confirmed that, yes, Tony wanted some "distance" from me.

I was diagnosed with bipolar disorder in June of 2009. In hindsight, I could see behaviors on my part that were less than desirable. It's embarrassing and uncomfortable to suddenly have insight into one's own undesirable behavior, but I have tried to just embrace and forgive that part of myself and to genuinely make amends wherever appropriate. I'm now very stable and have accepted my life.

Last fall I finally decided to take the bull by the horns and wrote Tony a long letter explaining and apologizing for the things I had done that might have upset him (I had to guess at what those might have been, as we are no longer talking). I got a "thank you for your letter" response, but nothing more. The few times we have had the opportunity to talk one-on-one, Tony asks me a lot of questions about my life, but does not share with me anything going on in his life, and that makes me feel overly scrutinized.
It is my belief that you should never share your illness with your friends. At the very least expect to loose them under such situations.