Selfish friends are fair-weather friends who turn up only when they need help. Selfish friends generally withdraw support when you are the most weak and vulnerable. One needs friends to share one's joys and sorrows with. Selfish friends desert you in your testing times when you are facing adversities and will surround and keep hovering around you in your prosperous times. One should stay away from such people and keep them at arm's length.
In life, only value those people who value you equally. You don't need to be vocal and expressive in front of people who don't value you a lot. Learn to keep things to yourself and try being a patient listener. Be quick and cunning enough to figure out selfish friends. Communicate and deal wisely with such people and there is no need to keep them updated with your life's happenings all the time. Dealing with such friends is an art.