One thing that will probably help with you losing interest is to simply break things up over multiple sittings/days. It's normal for interest to wax and wane, but there's really no reason you can't get up before you consider the lesson "complete".

To your question, I did mark the lesson as complete - so you can take that as a sign that you're doing well enough, and that you're expected to keep practicing this kind of thing, along with everything else, periodically as you move forwards into other matters. You don't have to sit here right now and grind away - you're welcome to move onto the 100 chest challenge.