I went through a somewhat similar phase in which I didn't particularly care if I lived or died (new city, shitty job which I wasn't doing well at, had no friend

I went through a somewhat similar phase in which I didn't particularly care if I lived or died (new city, shitty job which I wasn't doing well at, had no friends / gf, poor health, no immediate prospects etc). I think what helped get me out of it was focusing all of my available willpower and effort on one or two areas which were completely in my control and where success was readily attainable through consistent work. For me those were lifting and dieting, and those activities reminded me that I could be successful, reminded me that I had self worth, and boosted my morale. This created a positive feedback loop in which that success emboldened me to address other problematic parts of my life and create further success and happiness.