You know what kills my friendships is "Don't get mad, get even" in kind if that is possible.
A friend for example, I have forgiven several times before knowing I had PTSD (I understood why). Once I new what it was, I shared it with him and explained it to him with a story about a girl that kisses me. I was surprised to say the least, then she said, "You don't remember me,do you" I said, "No" her response was, "That's OK, can I go party with you guys?" I said "yes" Well my friend wigged out (his house) "Do you know this girl?" I said "No" We just left her while she was getting water in the back of the store.
Anyway I shared and we lost touch soon after. Honestly I don't think he is able to forgive himself or he is pretty pissed I didn't remember that pretty girl.
I keep friends at my interests, off roading and guitar playing. As far as buddies, I have my wife and family
PS: Now this girl, I've been able to have a few lunches with to explain my reaction and that I am very in love with my wife