I loved that calm sensation when it first appeared.
Several weeks into HRT I started experiencing these calm periods, at first for several hours, and then for days. It was amazing. The irritation that I had felt, sort of like the buzzing of a beehive, but not an audible hallucination or anything, just a constant background agitation, had been present and intensifying for decades. When it vanished at first I didn't recognize the change, beyond feeling really good, really calm, and able to drop into my daily meditation in seconds instead of 10-20 minutes of trying to calm and center myself.
I THINK this corresponded to the big drop in Testosterone levels. As my Estradiol levels rose I had an improvement in mood and energy, also appreciated, but the fading of this odd 'alarm' state from the back of my mind is the most significant, critical mental change I got from HRT.
This was the change that told be I was on the right path, that I could survive after all.