Yup, it's easy to push to the point where learning has stopped and frustration is building. We can always go back to a lesson and pick up where we left off. Learning, for me, doesn't always happen in a straight line. I kind of zig zag around, coming back and retrying those parts that proved difficult. Normally, over time, I get things worked out.
You will find a point, sounds like you might be there now, when you know it's time to give that lesson a rest and move on.
Good luck
edited
This year the diet is definitely gonna stick!
