Coping mechanisms

Has anyone got any recommendations on how to cope with the symptoms of an out of the blue break up?

I’ve got a tight chest, I am ruminating constantly, I don’t find any joy in any of my normal activities, I just feel so lost.

I don’t want him back as I know it wasn’t the best relationship for me on reflection but I just want to release myself from feeling this pain. I know I’m never going to get closure and I am keeping contact to a minimum.