The more you know, the more you know how little you know.
In the following two areas, I fail about 75% of the time
(to say nothing of all the other areas):
ONE: While not a constant problem, using literally figuratively still catches me out probably half the time. (I've been a proponent of Sentence First by Stan Carey since starting this blog. While his is not the first I've seen discussing this issue, it is excellent and thorough.) Of course, that half comes generally, though unfortunately not exclusively, from my total English usage, most of which is casual speech, during which times my grammarian self, weak as he is, is less vigilant. Though figurative literals is not an issue of which I haven't before been aware, seeing it spelled out so precisely and exhaustively fascinates my inner and pathetically dominant nerd.
TWO: This issue is brand new to me, and I am a little bit embarrassing to admit that, despite its glaring obviousness, I screw this up, as far as I can tell, 100% of the time. *groan* Regardless of my pride, however, it's exciting--and by this I mean, I love--to learn this crap, even, or especially, so late as my tenth year teaching. This is not the first English usage item I've learned via another's blog that will change the way I speak and write ("MISS NOT," at the ever-brilliant Language Log), and certainly, especially considering my general and ever-growing lack (a self-awareness issue, I know) of expertise in my professed area of expertness, will not be the last.
Cheers to learning.