I rarely have problems with friends because I know how they are and I know what to expect. Even my co-workers and managers, I know them so I know what to expect. I have sometimes been upset with one of my managers because of what she says to me or the way she speaks to me at times but the matter is dropped and... well, not forgotten but I don't harp on about it.
My dear best friend and I have had the odd misunderstanding. I got quite angry once because he often seems to forget or ignore what I tell him and in that instance I told when I would be home and that I would call him but he called my father four or five times asking where I was. Hackels were raised when I confronted him about this but seeing the situation was potentially going to get blood boiling I toned it down and we settled the issue.
Hey, I am not perfect and make mistakes. I want to be big enough to apologize when it's my fault and I am willing forgive quickly whe someone acknowledges their mistakes as well. I don't want to strain my precious relationships or live with a grudge for months.