What does this quote/phrase mean?

Your friends tend to tell you only what you want to hear and they tend to act in accordance with your wants and needs.

Your enemies will do no such thing. They will act within the boundaries of their own self interest. You learn from such people because they will at least be truthful with what they want of you. They will never be faint of heart and consider your feelings when they deal with you.

The loopholes that we have but have no knowledge about these become gradually crystal clear the moment our enemy/-ies start their enemical activities.For fear of the harm to be caused by enemy we start learning different new lessons which are really very precious.We become aware of our shortcomings in respect of our deeds, character & other related matters esssential for self protection.We become patient, start evaluating our idiosynocracies . We begin to see a new world of thoughts.

An enemy teaches you more about yourself than most others.There is competition between you.The enemy makes you want to prove yourself.An enemy can teach you perseverance and patience,to handle pressure and hold your ground.An enemy essentially changes you,usually for the better.

you learn more from the enemy as compare to what you learn from your friends or books or school teachers