I just clicked the mouse thinking about my best friend and I feel really bad now
Why were you thinking of your best friend?
I feel sad because I was remembering all the good times in our relationship since we fell out.
You two were really close. It's normal to think about your friend and remember good things about them.
I know, but I feel like shit because I didn't like the relationship we had. I wish he would leave me alone forever, but I know that I'm going to miss him.
Well it sounds like you are really conflicted about what happened. Have you tried reaching out to apologize to him? It might give you some closure.