Labeling and Mislabeling
This is an extreme form of over-generalization. Chances are you're involved in personal labeling when you begin a sentence beginning with, "I'm a..."
Labeling is not only self-defeating, it is irrational. Your self, your being, cannot be equated with any one thing you do. Your life is a complex ever-changing flow of thoughts, emotions and behaviors. Put simply, a human being is more like a river than a statue. Negative labels are simplistic and false. Would you think of yourself as an eater, just because you eat food? Or breather, because you breathe air to live?
Labeling is nonsense, but such nonsense becomes painful when you label yourself from a sense of your own inadequacies. When you label others, you will invariably generate hostility. A boss labeling his irritable secretary as an uncooperative bitch is a common example of generating hostility in labeling another. The boss now resents her due to this label. The secretary in turn labels him an insensitive chauvinist. This negative cycle repeats itself, with a focus on each other's weaknesses and imperfections as proof of the others worthlessness