Saying goodbye to friends is so painful to do. I remember reading A Purpose Driven Life, in which Rick Warren alludes to the fact that this is because we are "made to last forever." He says:

"This life is not all there is.
Life on earth is just the dress rehersal before the real production. You will spend far more time on the other side of death-in eternity- than you will here. Earth is the staging area, the preschool, the tryout for your life in eternity...
The Bible says, "God has...planted eternity in the human heart" [Ecclesiastes 3:11]...
When you fully comprehend that there is more to life than just here and now, and you realize that life is just preparation for eternity, you will begin to live differently. You will start living in light of eternity, and that will color how you handle every relationship, task and circumstance."

Perhaps the reason saying goodbye is so hard is that relationships are supposed to last. We were made to give of ourselves to others and for our friendships to be marked by an ongoing commitment. It is this kind of commitment which allows us to transcend superficiality precisely because conflicts do not mean the risk of losing the other.