I'm Disappointed...

Dear, it's very late here in the United States. I'm surprised I'm still even up haha! It's okay, I'm sure people will come around.

I'm not sure about "writing" here...

I'm disappointed...

There is no correction yet, so we talk about a correction that we just imagine. Any correction. Then it's "a correction".

If you have one or two corrections here and you talk about one of them, then you can point at the correction and say, "THIS correction" (or also "the").

Then you can talk about it somewhere else and write a third journal entry about it. Then you can't say "this", because "this" only refers to very close things. So then, it's "the correction".

Also possible:

I'm so disappointed that nobody corrects my writing...

"Nobody" is like "he, she, it", so it uses the verb form with -s.

Edit:

Listen to Nicole! :) Then, we'll have to take "writing" and make it "notebook entries". Or of course "what I write/wrote". :) See, now I learned something, too.