In the middle of the New York Times article on memorization the author mentions the OK Plateau, a place where things are good enough that you stop making an effort to improve. Several techniques for getting past the OK plateau are suggested, most notably practicing beyond your comfort zone. If you’re a professional pianist, you don’t practice the easy bits, you practice the stuff that’s difficult.
Now, to work out how this applies to agility training. I expect it means working on those tough weave entries.