Ask HN: How do you get past difficulty learning what's needed for a new job?

Ask HN: How do you get past difficulty learning what's needed for a new job?
27 by _sdegutis | 33 comments on Hacker News.
I have one client right now who pays me out of pocket, but the work he's asking is beyond my understanding. It's dealing with a new system that has a lot of parts. It's well documented, but when I read the documentation, it's just not sinking in, I'm not "getting it". My eyes just gloss over and I re-read the same sentence over and over for 3 minutes without any progress. This is the same thing that happened when I tried to learn Rails about 8 years ago. Is it possible to push past this and force my mind to learn new things? Is being 32 years old and in very poor health a show-stopper for learning new complex concepts? My first thought is to just get another job, one that I already know how to do. But that's outside of my control, this is my only client and will be for a few months. Any advice is appreciated.