There are two things, one getting yourself in health is good for you without having anyone see it but yourself. Two, if you catch yourself staring at something while simultaneously in dark thought, just do the Jedi mind trick. Work on the garden, call your daughter, watch some comedy...Bill Burr is one of my favs on Netflix streaming, or some show that makes you literally laugh out loud, or any show that will keep your attention. The point is to take your attention off of the dark thoughts and don't allow yourself to make a habit of that.
Since I have ADHD, my Jedi mind trick is the opposite. If I catch myself thinking about anything other than what I am doing I have to remember what I was focusing on before the last focus...sometimes before that one too...who am I kiddin' my life is one tangent thought after another minus the ones I can't remember