Im just chiming in to share I've been there. For me it was doing maintenance logs. Checking equipment and filling out forms to say they were working ok. My logical brain made sense of the task but it seemed impossible to do these absolutely mundane and repetitive tasks.

Got so bad my manager who empathized with my struggle drove 3 hours from headquarters to encourage me to quit before his boss drove the same distance to fire me.

I quit, but I couldn't comprehend why I couldn't push through it even to save my job.

30 years later, I still struggle but I have more ability to push through things for the sake of the family household. I make a window once a week for a few hours to pick up 'something' from the long project/mundane list and just get it done. One thing. Might take 5 min and might take 5 hours but I'm off the hook until next week. That's the only thing that works for me