It is inevitable, things will change. We will fall apart...

I recently took a different path in my life. It means that I don't see my friends every single day like I used to. I miss them a lot, but I can see how easy is to just fall apart and it makes me wonder. Is the constant contact that made us be friends? Is it the fact that we were in the same situation that grew a connection between us? What makes people be friends? Is it common interest? But then I always think of how different I am from my best friends. We share some interests, but personalitywise, we couldn't be more different somehow. However, I can see that in many things, we feel the same. Wouldn't that be the case for every normal human being or am I just being too naive? Is this enough? What is necessary to form a relationship, a friendship, a long or short connection between two people? Is is enough to keep it for a longer time? How much one have to nourish this connection to keep it alive? I once had no friends and nowadays I am facing the opposite problem. Somehow I managed to connect to a lot of different people and I love them all. However, how can I keep these connections in so little time? I was trying to think of how I would explain to my 12 years old self that I have too many friends. How could I even imagine that would be possible back then. And there are still so many nice people in this world that I haven't met yet. Should I stop? Am I suppose to keep things the way they are? I will try my best not to miss anyone, but it is inevitable.