This seems like a useful counterpoint. The idea of leaping in, realizing what you don't know, and then backtracking to cover the fundamentals seems useful. I recently decided I wanted to learn advanced math, grabbed some sample calculus problems, and failed them so hard that I'm now doing a methodical go-through of Algebra before I even try again.

I've found that, for some of the exercises, and realize I'll completely forget the material in a week because it seems "irrelevant" to me and is easy to relearn. For others, I just skim over them because I already know how to do it, or because it's simply irrelevant to what I want to learn. Taking the time to at least skim each section has definitely helped me, though, as I get little reward boosts of "oooh, I already know this!" and I'm making myself aware of skills I might need to review if they become relevant.