I get it. Lots of variables though.

If you use the Search feature you might find some of the older posts. There is one I found from Mark specifically regarding tennis balls.

I really hope you are able to get your anxiety about concussions lessened sooner than later. I hope you're getting some professional guidance about that. Keep working on it. There are many different ways of doing that as difficult as it might seem right now. It's very important for your recovery.