About Literature: Irrational beliefs?

So what's wrong with Doggie this time?

I wonder, when we read books, do we unconsciously learn how literature works?

This has been a long-time concern of mine, and I wonder if it should be. Maybe it's just mind over matter, just plain worrying way too much. So what is this concern? Believing that I can't improve on my writing. I liked to write since I was younger; so when I make a mistake, I use "love" as a force to regain confidence, and tell myself that I can change. But, it seems near impossible. Or just very far away.

I find myself modifying what I write too much, as I am not I satisfied. Or am I just scared? I think, "this sentence feels wrong". "This isn't like in the books".

Heavy composition, which has gave me (and others. So, an example was set) praise for excellent writing because I'm told to "show and not tell", turned out to be flawed, riddled with errors. When you do that for a long long time, you just can't break from it easily.

The technicalities of grammar are not my strong point; sometimes, neither is my word choice. I can write a sentence unconsciously, but can't remember the rules of it.

School was long ago. I didn't pursue writing (and reading) and did not stay fresh in it, but my passion makes me want to revise my mistakes.

So when inspired this? What caused me to beat myself up. Aside from criticism, I wonder over my memory. When I read, say, a single long sentence, and turn away from the book, I can't seem to remember it. I can't remember the structure of it. The concern is further increased by my apparent lack of comprehension.

How can I prove this "lack of comprehension"?

Or maybe I should ask, how can I prove myself wrong?