I go skateboarding. It clears my mind completely. It doesn’t matter that I can’t keep up with modern tricks or anything. It still puts me in a zen state of mind and being physically tiring it leaves me relaxed and not worried about anything.
Exercise is definitely part of it, but also the feeling of accomplishment and occupying the mind.
I’m sure other physical activities can do something similar, but it’s important to find something that fits you.