The first reason was that I was having a falling out with a mutual friend. I knew I wasn't 100% in the right and didn't trust my friend enough to recognize that I was mostly justified in my position. So I didn't give him the option to side with me.
The second reason was because, after 7 years, I had started to view him romantically. After considering myself gay for so long, admitting to myself I was bi/pan was difficult(especially because the ratio was so lopsided and I hadn't felt anything toward men for over 2 decades).