Yep, when you don't worry about getting it. You let go of all preconceived ideas of how you think it should be. The gap in learning, means, I probably know this but maybe I don't and I'm okay with it because I know the gap exist.
When we get off our backs about getting things right and stop giving meaning to something we don't yet know about we are an open book. The page is blank to write on. If you're preconceived ideas are floating around it's like having writing all over the page already and trying to make the new stuff fit.
When you continue a course after a break, it makes sense to think okay I might have forgotten something, it might even be important. Given that I might not understand 100% and I can be cool with that because my goal is to finish the course and if I only "get" 30% it's more than if I don't finish the course.
If you can adopt that line of thinking (which is easier I think if you just move on instead of listening again from the beginning) You'll get that 30% and I'll let you in on a secret 30% is probably all you need to know The real scorecard is in doing.
Starting a course is like climbing steps to reach a certain point. You can take in the vista where you are at. It's a bit daft to climb back down like a game of snakes and ladders because you stopped along the way. The vista does change the next time you view it and it's never as exciting as the first time. That excitement is reserved for the new vista.
Anyway, you'll find references to earlier parts of the course is enough to remind you of what you're doing.