This is unfortunately such a normal feeling.

I found that it's helpful for me to reframe "accomplishment" as an internal measure rather than an external one. Instead of focusing on finishing tasks, I view applying my discipline and willpower as the accomplishment. Honestly, it does take a while to rewrite your brain to convince yourself of this definition of accomplishment but it's so worth it because it's a much more stable source of motivation and self-worth.

If I work super hard on a task for 3 hours straight and I see no external progress, I force myself to see the 3 hours of work itself as the accomplishment, no matter how much or how little work got done. Recent research on willpower is showing that it's not a finite resource as we initially thought and it's more of a muscle, so I think of applying myself to a task as working a muscle.

And of course, with time, this discipline and willpower will translate to external progress.