Love does not allow walking away
People change and relationships change and the best of relationships can become suddenly painful but that is no reason to give up on them.
That is what love is about - seeing it through, holding to the relationship no matter what. Sure, sometimes you are not right in someone's life and they are not right in yours and the relationship may need to be managed to 'protect' you or to give you 'time-out' so you can continue to act with integrity and maturity, but walk away never!
A parent should never walk away from a child; a child should never walk away from a parent and none of us should walk away from family or old friends.
Another spiritual maxim is that those who can be a source of pain are our greatest teachers. I also believe people are more damaged than evil and more frightened than cruel. Sometimes they need space; sometimes you need space but Love is powerful enough to ensure that if you choose, the connection will remain until they or you are beyond the times of pain.