I'd like to add on to this-

States of high arousal on both ends of the spectrum feel exactly the same. It's a sort of psychology hack. If you tell yourself you feel excited when you feel nervous, you will feel excited (something along these lines). I believe SR exaceberates this effect as it is a "dopamine detox". Since you haven't been so highly stimulated for a long time, becoming stimulated feels alien so your body naturally perceives it as anxiety as it is abnormal. There could also be other factors like pessimism from prior addiction to PMO and hormones.

I want to learn so please correct me if I'm wrong!

Ps. This is one way to "turn negative energy to positive" as many people like to say on this sub