I think that there is a natural impulse to attack others to correct them.
I believe that this is why bullies feel so much pleasure terrorizing others: they believe that they are "curing" the other's weaknesses with violence. They feel a biological reward by bulling people.
I feel that I choose my friends by how much preassure they apply to certain parts of myself.
If I am too day dreaming I need friends to wake me up.
If I am too introverted, I need friends to apply a gentle pressure to bring the best of my extroverted self.