yitzymotcha and big deal,
Thank you for bringing some psychological insight into the mechanism of anxiety.
I don’t have a background in psychology, but you are in effect asking a kashya on the Mesilas Yeshorim quoted above, and I would like to try to answer (unless you can explain to me that I’ve misunderstood the MY). Would be very interested to hear back from you.
Imagine a girl who was very nervous about being assaulted on the way to school, even on the main road in a safe area, where there is no rational reason to worry at all. As you say, her anxiety is a physical thing, possibly caused by chemical imbalances etc, and of course you can’t “talk yourself out of a fever”, so just thinking about bitochon won’t help, as you argued.
However this same girl has a different eitzo: that her father should walk with her to school. Her father is a tough big 6 foot fellow who has of course looked out for his daughter his whole life. She feels perfectly safe and secure in his presence and doesn’t feel at all anxious when he walks her.
Now I assume you’ll agree that as physical as anxiety can be, it nevertheless makes sense that even someone with these chemical imbalances would be able to stop worrying in such a scenario. And the reason is, this isn’t the same as trying to be rational and stopping worrying about whatever, where the ‘scary voice’ can politely disagree and get her worried again. This is different because the whole situation is different, its a situation where there is no place for her anxiety.
Well then, if we would really feel that we ARE always walking with our Father – if we would really really feel that way – there would similarly be no place for anxiety.
Obviously as I wrote earlier it is very hard for us to achieve such a level of bitochon, and the psychologists’ methods may be more achievable. I also think that bitochon is best learnt by example rather than from seforim, if everyone would have access to a role model in this area it would be easier to see how bitochon can counter anxiety, saying Tehillim a lot is I think a bit like having a role model, as it shows us how Dovid Hamelech applied bitochon in his life. However difficulty aside, as this is possible, the Mesilas Yeshorim is meyushav.