You might wonder why we flip out over stress the importance of accurate grammar and usage. Well, there are a couple of reasons …
You look silly or unprofessional when you don’t get it right. Don’t think the proofreading police aren’t watching. They are. And they never sleep.

Great writers not only struggle with their words and getting ideas down on paper accurately, but with fine tuning everything — including their usage.

Sharpening the saw in the small stuff is a healthy habit for writers … no matter how long they’ve been in the business. — Copyblogger.