Prior to the brain event, I am one of those people who thought that we all have at least some control over the way we think and feel[.]
As a guy who has done zazen (zen meditation) daily for the past 20 years, I think we have less control than you might think. This isn't to lean towards determinism. (Zen would reject both sides of that coin, so I would too) We can take control, mind you, but most people don't. Well I don't want to offer possible judgement on anyone. That can take control might be very very difficult in many cases, but it is usually possible.
But anyway, it's not a matter of willpower, nor even of habit, it's of not paying attention. A thought arises in the brain, the result of habits of thinking or triggered by some internal or external event (our stomach grumbling, the doorbell ringing, etc), and we just run with it without ever examining where the thought came from or if we ever agree with it.
Well, that's my idea anyway, but I could easily be wrong.
Anyway, I apologize I sometimes miss your writing so if you mentioned the stroke before I didn't see. I hope your situation improves.
As said, I used to think we had more control, but I assume we have almost none these days. I think that we are also differently equipped naturally to handle these kinds of things, so what might work for some, will not work for all.
I also think that similarly, our ability to "pay attention" is going to be largely determined by things outside of our control. What if for example, the people who can successfully meditate, can only do so because there is a switch in them that allows it, whilst others are missing the switch? How to ever know?