Yes, I know that feeling well. I used to relate it to being a robot with a switch on my back that I could just turn off. I'll give you the short answer for now, but things change. There might not be a way for you to positively see that currently, but, it may just help temporarily to do what ever you can to get your mind off of the situation or get through the day. That's what I used to do.
What actually happens is the more you can endure, you slowly start to build your mental strength over time, like weight lifting for the brain and emotions. You'd be surprised what you can do when you have to, so don't underestimate yourself. I know, blah blah blah right? Try to do something you enjoy to finish today or just get some rest. Maybe tomorrow your outlook will be a little different? Day by day, small steps, you can only do what you can do, but do it. All I ever ask of myself or anyone else is do the best you can, and you've got my vote. Hope that helps, peace