How do i stop thinking about stuff that are over?

I had a falling out with some friends and that's because of a single person that belongs among them. For quite a while now I had set my mind that this friendship is pretty much lost. The reason I had that falling-out is because that specific one friend was very toxic against me and is very toxic against other people that with time tried to fit in our gang, and the other friends from the gang just won't see it. So i walked out of that situation, leaving a big strong text response behind me (in a post that toxic person did for me in our fb group page) that is supposed to close the matter, and it majorly did just that. But the people involved do keep commenting there still, Mainly to say something negative and toxic and without meaning or a way to further the matter. I was kicked out of that group (the admin of that group is the toxic person) but still continue to receive notifications which now I have hidden and deleted. I am pretty much committed to it I decided to move on and find a better place for me to fit.

And here's my question: how do I move on without these feelings destroying my insides? I feel terrible i've known these people and have hung with them for 4 years, and all I can think of is I don't want this situation to be as it is, but there is no turning back, or reason to unless they change. I don't want to suppress it. I want to not care about it anymore because it's over. All I do is replay the same arguments in my head as it did take some mental strength to do it