It's interesting how people come and go in your life. Sometimes you meet someone and you think nothing of them and then you never see that person again- but then sometimes later on in your life that person becomes a huge part of your heart. It makes me want to go back in time and whisper in my ear, "Hey look, pay attention to this guy (or girl) your introducing yourself to- he's going to mean something to you one day."
The best friends I have ever made have been instant. The kind of friend you just know right from the beginning- there's no awkward get to know you period- you just know them. Other friends have taken years of knowing them and being with them to develop a close relationship, and I do feel close to them but never as close as those friends that touched my heart instantly- I don't think they will ever reach that level because its just not even the same kind of friendship.
And sometimes you lose people.
Sometimes you have a flash of brilliant adventures with someone who you love instantly. And it was one of those instant friendships but that instantaneity is true throughout- for it only lasts but what seems like an instant in time, and then they are gone, off to do the next great thing in life and meet the next great friend, just like I am. I never second guess why this happens, I know people come and go, I know sometimes (no matter how great the spark between two people) you were just meant to be in each other's life for a short amount of time.
You never know though, so look at every person you meet- really look at them and appreciate your moment with them. They may stay, they may come later, or they may never come again, but either way you should know them.