just be nice... it's not that hard. life really is too short for being moody and unpleasant to people who don't deserve it. conserve your friends, don't make needless enemies just because you happen to be in a bad mood. the people you think don't mind (or maybe just don't matter to you that day) sometimes really do. the people who pretend not to be hurt by your continuous mood swings may just be better at concealing it than others. the world is bigger than you, regardless of how much YOU love YOU.
(most of us just see a mean girl.)