I completely understand the losing a friend because of them just not caring about you anymore. Your statement its not our place to make excuses for another's behaviour is brilliant and very true and I will remember it.
I have recently had to say goodbye to two friends that have been behaving enormously strangely toward me and even after months of trying to do "repairs" nothing helped. It was a case of its over, get over it. The last thing one of them said to me was "I have nothing to say to you." Wow - It was not like we were having a fat argument, I asked her if she was okay - because a mutual friend noticed how 'weird and fake' she was behaving and came and asked me to find out what is wrong because she reckoned she would definently confide in me since we were "such close friends". Well unfortunately not anymore. After months of rejections and outright lies I decided to let it just be. I think I'm still going through the grieving process but since they wish to be out of my life its going a whole lot easier. Our mutual friends though took that steps ages ago and are also "just leaving them alone".I wonder sometimes how people can just change like that you don't even notice until its right in front of your face....
Looking forward to reading more of your posts!