Things change

Many things chance during a lifetime, the biggest ones being people and yourself.
People change, they are not the same person as they were in primary school as they are in high school or as they were in high school as to who they are in college. As people get older they change to fit the circumstances that they are in, they change to fit into the environment that they've been put into, the fact of the matter is that even if you know someone and get on with them that might not be the same case in years to come. Don't get me wrong people can be friends for a lifetime and that's absolutely great but unfortunately in some cases it doesn't work out like that.

Now you, yourself are just like everyone else, you may have your own unique style and have unique qualities but you still change to fit in, you aren't the same person you were 10 years ago and you won't be the same person 10 years form now.
People and yourself change and that's just something we all have to live with because absolutely nothing can stop it from happening.