I am sure everyone has at one point received the email describing how friendships are defined by a reason a season or a lifetime. Every time I read this article I think it seems to apply to different people in my life. I believe that the friendships you choose to keep throughout your life are the ones that help define you as a person.
Friends are here to challenge your growth, to support you, to teach you, to become a part of you.
(found here: http://www.naute.com/love/reason.phtml)