Is it ok to not be a friend to a friend without them knowing?

I've been thinking about friends and other friends and their stories about their friends, and I couldn't help but wonder....

"Can you stop being friends with your friend just cause?"

Just cause you have a difference in opinions, just cause you have different priorities now, just cause the jokes doesn't seem that funny anymore... just cause you've moved on but they haven't... or is it your fault you're feeling this way?

Why do friends fight? Doesn't it start with a little misunderstanding that someone just thought of it as a big deal? Isn't it? I wonder how those friends become friends again... Quite intriguing...

How can you be friends with someone when they haven't tried anything to keep in contact with you? When you did try to reach out but all you got back was dead air... Is it still your fault to feel this way? I wonder how many chances you're willing to give, how many jokes you're willing to fake a smile, how may times you have to suppress your feelings so you don't hurt someone else's, how many conversations you have to start, drive and finish...before you realise that the same topic comes back and you all laugh at the same stupid joke as the last gathering...

When you're feeling down and sad and you try to talk to a friend and they don't respond back.. how should you react when they don't have time for you but you have all the time for them? It doesn't necessarily mean that they are important for you than you are for them..... Or is it?

Friends they say complete the other half of your wing so you can fly together... Uhm... Sure... What if they take your wing with them and they fly away with out you?? What would you do??