Franz Snideman, RKC recently had a baby and that got me to thinking back a few years to when I myself was a new dad. I don't know how most fathers process the whole experience, but one thing (of many, of course) I enjoyed was watching my son develop the prerequisite strength and coordination to stand up and eventually walk.
Seeing babies learn and do complex skills with very little direct teaching is inspiring to me. Before my son had stood on his own for the first time, or taken his first step, he had already done leg lifts, "superman drills", "sit ups" (of a sort), and elementary tumbling for repetitions numbering in the thousands, possibly tens of thousands. Would an adult have the patience to do this? How long would a grown-up perform elementary "drills" before trying to jump into "the meat and potatoes" not even close to being ready?
"Weakness training" is what most intermediate trainees need and avoid like the plague. Some of this is conscious and some of it is unintentional. The key to finding weaknesses is challenging ourselves to different stimuli often enough that we don't lose the functions we spent so much time (or didn't...) developing in our formative years. The trick from there then is improving those uncovered weaknesses without losing training focus.