I had a similar problem, but for different reasons. There was a lab that I did end up failing and I knew I would, but the tasks were just so insurmountably and needlessly time consuming and boring that I couldn't rationalize even making incremental progress on them. These labs involved essentially manually drawing many graphs related to climate phenomena, and it's just not something I could bring myself to do. I'd literally sit down, look at the assignment, and then pretty quickly drift off to sleep. This was for an unbelievably easy intro class that I was taking in 3rd year, and I failed it, much to my profs disappointment, because the lab component took something like 50% or more of the grade. I didn't even show up for the lab exam. This is also despite the class being interesting, the prof being great, me having a lot of enthusiasm for the subject matter, etc.. it just didn't work.

I've since been diagnosed with ADHD and take it to get through a lot of days where I'd otherwise be non-functioning, but for the life of me I don't think I'd be able to do those assignments with any amount of meth in my system.

That might not be a helpful story. I wish I could relate in a closer way, but I don't really connect very well with anxiety related fear, unless it involves speaking a foreign language in front of the class or something. If you're struggling with anxiety in general, I might recommend getting into skateboarding, unironically. There's nothing like eventually pushing yourself to try something many many times and failing in front of other people, often only to have them cheer you on in a uniquely supportive way.