A quote from Leo Tolstoy, quickly emerging as one of my favourite writers of all time:

One of the most widespread superstitions is that every man has his own special, definite qualities; that a man is kind, cruel, wise, stupid, energetic, apathetic, etc. Men are not like that. We may say of man that he is more often kind than cruel, oftener wise than stupid, oftener energetic than apathetic, or the reverse; but it would be false to say of one man that he is kind and wise, of another that he wicked and foolish. And yet we always classify mankind in this way. And this untrue.

Men like like rivers: the water is the same in each, and alike in all; but every river is narrow here, is more rapid there, here slower, there broader, now clear, now cold, now dull, now warm. It is the same with men. Every man carries in himself the germs of every human quality, and sometimes one manifests itself, sometimes another, and the man often becomes unlike himself, while still remaining the same man.

Related: Two Conflicting Rosebushes