The Words We Wield

Dear Readers,
  You can tell how deep into a novel I am, by how often I blog. See, right now I should be working on Chapter 20 but Chapter 20 involves a LOT of backstory, and description. The backstory isn't so hard, but description.....WHY am I so bad at description? I see it in my head, and just have trouble translating it onto paper. Why is that? It's infuriating, I get so impatient and just write trash. (And not like trash-on-its-way-to-becoming-good-writing, I mean trash.)
  Okay, Okay, I'm going to try to get words down.
Thanks for stopping by,

KR