I've been feeling like this for all my adult life. Every time I start to get my life together, make strides to improve my health, excercise, diet, organise my work etc. the asshole inside me takes a hold and drags me back to zero. I'm there again.
I had a week, running regularly, starting back into the gym, lifting weights, trying hard at work and generally seeing how I could get my confidence back. It was a hard struggle, but I pushed through.
Then today, for no reason whatsoever than that my mind doesn't work right, I'm back in the pit of darkness that I worked so hard to claw myself out of. I hate myself, I have zero hope for the future and I have worked out that there is zero point in bothering to even try and fight this nature. It's who I am. I'm destined to live miserable or not live at all. No point in fighting it, because it always wins.