If friends disappoint you over and over, that's in large part your own fault. Once someone has shown a tendency to be self-centered, you need to recognize that and take care of yourself; people aren't going to change simply because you want them to.

Compliments win friends, honesty loses them.

I distrust the wisdom if not the sincerity of friends, who would hold my hands while my enemies stab me.

A real friend or mentor isn't on your payroll.

An insincere and evil friend is more to be feared than a wild beast; a wild beast may wound your body, but an evil friend will wound your mind.

I suffer from girlnextdooritis where the guy is friends with you and that's it.