I found that dosage of Sertraline made a notable difference for me. Too high a dose would get me in a hypomanic state. That may be where you were at when feeling superhuman. But mania can't last forever and is inevitably followed by a low.

Stopping cold turkey was bad news for me, too. I got the "zaps" any time I turned my head. So, I decided to taper down, which worked fine.