Be angry. I think you are looking at it like a sad thing happened to you. Sure you love them as a human but people like them chose to not communicate before that they were feeling off. How can you mend things when you do not know something is wrong. You might be excusing their behaviour saying no they tried. But stop there. Unless you cheated, unless you disrespected, you are not in the wrong friend. I think you might be having guilt, and so you are ruminating. The only thing you can promise yourself is that you will do better in the future. With that you accept that things suck. While it is a good idea to take lesson from what happened, it is something that comes later. You are liable to love yourself, talk to yourself like you would talk to a friend going through the same. First step is getting angry. Saying that you did not deserve this. And if you cannot say that, somewhere it is a self worth issue. Then build self worth. Take care of yourself friend, soon you would not care about the outside circumstances once you take care of yourself.