Something about the subject or about your protagonist, whose head and heart you must inhabit, is notably different than anything you’ve handled in your previous stories. Put the WIP away. Maybe just for a while, maybe forever. If it niggles at you, come back to it fresh and perhaps with emotional walls in place. Then you’ll know definitively if this is a story you must write: you’ll either finish it without the extreme response, or the anxiety will flare up, confirming the decision to let it go. You wouldn’t be the first writer to put the kibosh on a project. That’s not a failure, and it’s not starting an unproductive habit. Writers invest themselves emotionally, poking at questions and issues relentlessly so as to explore them and affect change in their characters; we can’t always know what can of worms we’re opening. If you’re finding this investment to be intense in a way that’s unhealthy for you, it’s okay to poke around elsewhere—the human mind has a million enticing recesses to explore in a new thriller.