There is a fill-up effect (what you describe) and a build-up effect (repetition on the long run).
It's like a capacitor discharging[0], so at first you have to recharge it often† to not go under the anxiety threshold, but with time it holds more charge, and charges better, so it discharges much more slowly thus reaching the threshold much less often, if at all.
† Part of why it may be important to workout for shorter times/intensity, but more often.
It's like a capacitor discharging[0], so at first you have to recharge it often† to not go under the anxiety threshold, but with time it holds more charge, and charges better, so it discharges much more slowly thus reaching the threshold much less often, if at all.
† Part of why it may be important to workout for shorter times/intensity, but more often.
[0]: https://boolscott.files.wordpress.com/2009/12/capacitor-disc...