Not only it's good to lose some friends, but it is also a healthy habit which can save you the trouble of dealing with unrealiable friends.
I really enjoyed reading your post. I lost a lot of people throughout the years for various reasons. Some of them were really close to me and I had this unrealistic expectation that they would feel the same about me. It was very painful to see that we weren't on the same page but I moved on. I didn't regret any of the things I had done for them. They played their role in my life at a certain moment and that was it; lesson learnt.
To some I offered three more chances just like you, while to others who were more dear to me I told them bluntly how I felt. Most of them assumed that my sudden confession/complain was a mood or that had something to do with my illness (which they never bother to ask or learn more about it). I told myself it was their loss, not mine.
Nowadays I have only a few close friends that I can rely on anytime for anything.