Change.

The world as I see it is ever changing, growing, and expanding. And we live in the world, so I guess it is like us to do the same. I have only lived seventeen years in my lifetime and I hope to live more. But more and more I go through life and notice something:
As you live, things change. Change is something that I have come to hate, and it always leaves you missing the good old days.
"I wish there was a way to know you were in the good old days before you have left them. . ."
~Andy, The Office.

But it is true. You never know what you have until it is gone, that is life, and that is change. Life always looks better in retrospect, and that is nostalgia at it's best. 

"Nostalgia is a file that removes the rough edges of the old days"

~Doug Larson

I find it is good not to rely on the past though. However it is hard when the end of a chapter is near and you can't help but look back and regret things. Things you did, things you didn't do and things done to you. But, I think there is one important thing. I would not give up anything I did in the past. It has made me who I am today, and I am thankful for today. I find that this is the key to change: living now, in the moment. So long as you live in the moment, everything does not matter anymore and then, in that moment:

 "The past is history, the future is a mystery, but today is a gift, that is why it is called a present"
~ Master Oogway, Kung Fu Panda

However life goes on, and Just as:"You never know what you have until it's gone,you never know what you want until you have it."

~Elaine Sheehan

 So we must press forward. To anyone dealing with change, to anyone who wants things to stay as they are:

"Take heart, fair days will shine!"

~The Pirates of Penzance

Seriously, have faith that everything will work out. Things always have a way of working themselves out in the end. God has a plan, he doesn't want any of us to be unhappy. So rejoice and hope for a better future. I believe that life is about the relationships you have with the other people in it. Otherwise life might as well be meaningless. If it was just you in the world, wandering, that would suck. So, get the most out of life as you can. It may hurt along the way, but that is life, working toward a better goal.