Re-learning how to learn is a critical factor in your progress model. To be successful at learning a 'new' thing you need to reflect and document your progress. You need to ask yourself,"Why am I not getting this/why can't I recall that/ Have I made any progress..." In US education systems students aren't typically taught to critically self-assess their progress--yet that is the only way to progress as you've suggested.

At 68 years of age, I am learning to play piano- one day, one hour, 10 minutes at a time, and I see progress!

Thank you for your reminders to stick out the frustration and keep on learning new things.