friends come and go

years from now, what is the assurance that the relationship we built with our friends won't be damaged by the time?just like now, a year, 2, 3 even 4 years ago we used to have a friend that no longer today, due to several factors, miscommunication, misunderstanding and most of all changes.
we loose a friend when we loose communication, it is important to a relationship to have a communication to understand each other and to know what is happening to each and everyone.
if we got ourself into a trouble, fight or argument, our friends stands behind of us, some do the talking for us, some makes us strong by their presence and support without talking, some discourage us to get into trouble, but what if we had a misunderstanding with our own friend/s? lucky if both are open minded and eaten their pride to clear up the misunderstanding, but to those who are narrow minded, no friends can step on their pride, pitty for them.
as an individual we need to grow, but what if our friends didn't? or were the who didn't?a relationship is a give and take process, we neutralize our personality and characteristics to blend with others, and they do as well to blend with us, but what if one refuses? how long can you tolerate their selfishness? and sometimes it's better to leave them for them learn.
and what the biggest factor?
US!
why? cause if we let things happen, contiously and uncontiously we wanted it to happen.