I started Foundations and Handstand a couple months ago, was too inconsistent during holidays, then started back up at the beginning of the year. Just "mastered" HS/PE1 and accompanying wrist work. Thought I'd summarize my experience in case it helps others:
First couple of weeks: Felt way too easy. Thought about jumping ahead.
Next couple of weeks: OK, I can feel this in my wrists now. And a little bit in my shoulders.
Next couple of weeks: I get it now. I've never felt fatigue in the wrists before. And there's no way I'll be able to do 5 X 60 sec. holds in HS/PE1.
This morning, after nailing the "mastery": That wasn't so bad. Thought I would struggle more.
Moral of the story: You have to trust the process. The slow progressions work if you stay the course!
Now, my RC/PE1 did not work out so well, so I'm having to back off a bit and go through some progressions again.....