I am regularly surprised that I can "do Japanese" to any degree at all.

I pick up a book, see 躊躇う (tamerau, hesistate) and somehow — ironically, without any hesitation whatsoever — know what it means and how to pronounce it. How is this possible?

I think part of the reason I feel this way is because I can only clearly remember learning a very small percentage of the total Japanese I've absorbed.