Just friends

Recently I got asked out by a male coworker but I told him I just wanted to be friends. It makes me feel terrible due to my reasoning behind the rejection but he is an extremely nice guy. Unfortunately he has bad mental health issues and doesn’t take care of his health like he should. For instance, at work he will make small jokes about suicide daily, he hardly eats anything, and constantly consumes energy drinks. As someone who already suffers from mental health problems for most of my life I don’t want to be in a relationship with someone who triggers mine. During work his I can tell his joke would trigger mine every now and then. I know he is getting professional help but I feel like a bad person for judging someone for something they can’t control. Even though I know that it was the right call because I should protect my own health and not have to worry about keeping someone else’s mental state stable along with my own.