I had a friend once in IIT who was a v close friend. We used to hang out together, lots of laughing, lots of jokes, but also sharing secrets, and doing projects together. It almost felt to me like we were siblings, we were that close.
But then one day, I did something to piss my friend off, I don't know what. Cause my friend never told me, just got angry and stopped being friends. Now my friend doesn't talk to me, doesn't tell me whats wrong, doesn't dance with me anymore, and come and hang out with me in my lab, doesn't even pop in to say a hi when I return from a 11 day holiday, and leave chocolates on the lab desk ...
I have many other friends, but each one is special, and losing one hurts. Especially when you don't even know what you did wrong. I would go and say a "Sorry boss, I didn't mean it, and please forgive me - your friendship is more valuable to me than my ego", but I don't know what to apologise for cause my friend never told me. Not knowing hurts even more.
I had a friend in IIT once, who isn't friends anymore - just a classmate now, who says hi and bye and no more.
And trust me when I say it hurts.