A wise man gets more use from his enemies than a fool from his friends. - Baltasar Gracian

In my own life, I've learnt so much about myself, especially about my weaknesses, from the people who couldn't stand me as a result of them. Your friends will love you in spite of your faults, oftentimes not correcting you when they should, because it's more comfortable for everyone if they just let it slide. Your enemies, on the other hand, have very few qualms about making their displeasure known. Sometimes that can serve as a necessary reality check.