Letting Go of Chapter Friends

In every chapter of the book called life, we go to new places, learn new stuff, aim for new goals, even meet new acquaintances. Some of these acquaintances could become new found friends. Friends are there to help you through a particular chapter. They could help you in different ways. Some help you directly when you are in need of help. Some gives ideas on how to pass through a particular task. Some are there to teach you lessons (even if it is painful). And some are there just to give you company, share life stories, listen to your stories, share with the laughter, or share with your pains.
But immediately after a chapter, many of these friends dissapear. But those who do not dissapear, I call them "lifetime friends". they stay connected to you even if you met them a couple of chapters ago. May be you don't see them for a while, but once you get a chance, you connect to them again or they connect to you again and treat them like the connection has never been broken.
Those who do disappear, I call these friends "chapter friends". After you move on to a new chapter, you don't see these friends again. Maybe for a while. Maybe forever. When you cross paths with them again in another chapter, the connection is not entirely the same. You smile to them, say "how do you do?" half heartedly and then walk away.
Every time I close a chapter, I feel sad for losing my chapter friends. Friends I lost after grade school, high school and college. Friends from my previous work, previous projects, clubs and organizations. Right now I have just finished my "Malaysia chapter". I already missed them. Some of those connections, I tried to rekindle. But a couple connections already ended in disappointing manner. Maybe I was trying too much or hoping that much that the connections we had would not change. I think I should just accept the fact that they are indeed chapter friends and they would want to go on with their lives, marking me as their chapter friends. They are appreciative that they had been my friend for a chapter but would appreciate more if I don't bother them on future chapters.
Right now, I am sad for my previous chapter friends, knowing that I might never see them again. Yet I should be excited that a new chapter is coming and I would meet other chapter friends and life time friends.