Heal

Evil Space-Gods want to enslave the Earth, and so transform some humans into soldiers in their army of subjugation. The problem is that the Space-Gods are so alien they can’t directly talk to anyone. The best they can do is fiddle with someone’s limbic system so their emotional responses are scrambled, then grant that person super-powers and watch them run amok, spreading fear and chaos.
There would be many kinds of emotional dysfunctions, as well as many kinds of super-powers, corresponding to humanoid monsters from myth (werewolves, vampires, zmeys, wendigos off the top of my head).
So for example the hero of the story wakes up to find they have been given super-strength and a taste for human flesh.
The hero then has to use mindfulness and rational thought to recognize and control their urges.
The first line: “On Saturday I woke up as a monster. I didn’t realize it at first. I thought I was just hungry.”