Read literature with an old writing style, especially if you dislike said writing style. The more opaque and complicated, the better.

I find that I'm a very fidgety reader, unconsciously skipping words, or even whole sentences, skimming over words I don't actually know the meaning of, and failing to connect the context of words that I do know the meaning of with the rest of the narrative or lecture. This I do with both literature and more importantly, when reading science. I've decided to read At The Mountains of Madness and penalize myself for every time I lose track of the narrative, and reward myself for every time I recognize when one sentence adds or contributes to something implied by another sentence earlier on in the paragraph, and so on. Furthermore, I will do this for only literature, and not with learning new scientific concepts, or even old ones that I have already learned. The problem is with reading comprehension, not with understanding concepts, and exercising two skills at once prematurely may cause problems. I hope this will instill genuine patience, so that being careful and observant becomes a natural thing, rather than the uncomfortable thing I wrestle with.