Life is all about finding the right friends. Unfortunately, this does not always work at that you find them right away, but it takes time. When you go away to school, this is the ultimate eye-opening experience to see who your true friends from your hometown really are. Also, every day you are constantly realizing who your real friends are, and who the are the friends that are constantly supporting you and have your back.
Unfortunately, there will be people you come across in your life who you befriend, who turn out to not be the best of people. This is necessary, I think, to becoming more mature as a person. If you meet someone who turns out to not be the best person, at least to be in your life, you can take away from it as a learning experience. This is important to understanding yourself, because in the future you can make sure you do not put yourself in a friendship if you believe this person will not always be there for you.
Upon going away to school, for example, you will also realize true friends from artificial friendships. When you live in the same hometown, seeing the same people day in and day out, you are bound to have some sort of friendship or acquaintance with these people. When you go away to school, or move, you realize who your true friends are when they are the ones who maintain contact with you, and care how you are doing. Not all friendships that end for this reason end badly, but its just a common dying off which is OK. You do not need to constantly try and keep a friendship with people who lack the interest or care to put forth a few minutes a week to talk with you. Life goes on, however.
Friends are important to have, and it is important to have those friends that, no matter what, will have your back. There reaches a certain point in someone's life, I feel, as if you finally mature and realize it is more important to be someone with 5 or 6 really close friends than the person who is friends with EVERYONE. It is more important to have genuine friendships, than tons of friends who only want to talk when it is convenient for them.