Dovv:
I have a couple of nits to pick with your post.
I agree with you that focusing on bitachon can negate anxiety.
But, doesn’t that sort of assume that the source of the anxiety is a lack of bitachon?
If the source is just regular psychological sources, then wouldn’t it be better to deal with the sources, than to try to treat the symptoms with bitachon?
(After all, goyim who have no bitachon are capable of being perfectly happy and non anxious.)
You also mention that one can focus on the worthlessness of this world and how it is only an antechamber to olam haba.
In my opinion, that is usually a source of anxiety for yeshiva guys.
Anxiety in the frum world, is often very tied to religion. You usually find it in people who have had “the fear of heaven” put into them, in unhealthy ways.
For such a person, focusing on those maamrei chazal about the obligations we have in this world, and the impending judgment, can be very counter-productive.