Getting frustrated studying for a certification

I signed up for a class from Udemy. Udemy makes tech classes you take at your own pace. The lessons are many short videos with lectures and some practical exercises.

I signed up for a class that will prepare me to take a certification class for a skill that will help my resume. Complete worth it.

I am about 2/3 done.

The thing is I've getting frustrated and mentally run down.

The course is voluminous. The going is slow.

I know the thing to do is to forget about finishing, forget about the results, and just focus on enjoying each lesson in the hear and now.

I enjoy taking notes, I am good at it, and I find reviewing notes to be soothing/meditative.

I still get frustrated and demoralized.

Worse, I always thought if I got a lot of time to learn something I would sit down at it 8 hours a day and blow it away. I get wiped out at about 3-4 hours. I'm kicking myself for this which isn't helping.

Any advice, commiseration, or success stories?