I think that logically you dream of either things you want, either things you fear. However as we say above, some things are subconscious, you don't always dream of precise objects or persons.
I once dreamed that we were 3 knights and we had to battle against 3 other giant knights in an isolated fortress surrounded by water. My 2 allies got killed, and I decided to flee by jumping in the water, where they couldn't follow me.
Someone told me from a dream dictionary that the fight represent that I want to defend my principles but I have difficulties in that (opponents are bigger than us). Me being the single alive is my need of winning, and apparently jumping into water is related to sex. There was more but I didn't remember everything.