For me, the closer I am to someone, I find myself becoming more
mean/selfish, cause I subconciously am aware that I no longer have
to impress them.
Sometimes, I also find myself becoming more bored with their
antics and behave a little coldly if its something that irritates
me, which wouldn't happen if I wasn't quite as close as I would try
to smile and take it as a joke.
However, the closer you are, you'll realize you can iron things
out easier and compromise, and there's a much higher tolerance
level and forgiveness.