We are sometimes forced to make a painful but inevitable decision to sever relationship with those who once were friends or those who we thought were friends. I have done so several times so far. There have been several reasons for this difficult decision.
The first reason is that they could not appreciate the differences between me and themselves in very essential things in life, criticized me according to their one-sided viewpoints and even tried to force what they believed was right. I and they may have made friends earlier in life when we had many essential things in common, but we are liable to change and have changed, with an ever increasing unbridgeable gap between us. We do not have to agree with every one about everything. But we can at least agree not to agree. With people who cannot do so there is no other way but to sever relationship.
Another is that the relationship became too one-sided. They contacted me only when they needed me, often making rather egocentric and insolent requests, but when I contacted them asking for help, they simply ignored me. When I realized that this was not friendship but unilateral exploitation, I simply ignored them.
I also had to sever relationship with those who broke a promise or promises that were very important for me, and worse still, did not even apologize for this. Friendship is and must be based not only on mutual respect but also on mutual trust. Once we lose trust in someone, our relationship with him or her cannot be the same.
No less unbearable were those who simply did not know how to behave not only toward me as a friend of theirs but only toward everyone. It is true that there are cultural differences, but there are things that seem unacceptable anywhere beyond cultural differences. It is not enough that they are intelligent and inspiring, unless they know how to behave as human beings.
Fortunately, I have not had to sever relationship but with only several people for one or more of these reasons, and I do maintain long-time relationship with many people. But once I see that someone who I thought was a friend puts the last straw, I do not hesitate to stop remaining in contact with him or her, ignoring him or her in the future. Inertia and positive memories shared in the past are not enough to maintain relationship.