Appreciate your friends while they are in your life, and thank them for making you a better person. When the time comes for you to part ways, cherish the good times you had together and the value that they brought into your world.
This deepness comes from years of making and losing friends, usually not of my own accord. Don’t think that I’m all happy that I’m no longer friends with certain people. I do miss them, and I’m hurt that they left me. However, one should reflect, digest and move on to new experiences and new relationships.
Also, if your friends are not making you a better person, but instead are pulling you down? You need to think about why you associate with those people, and if that is really how you want to live your life.