You’re coarse, of course. It’s just the way you are.
Coarse is an adjective that means rough, indelicate, unrefined. That’s you, of course, right?
Course is a noun — a route, or a sequence, an option, an action, a passage. Or a class in school. Not necessarily coarse, however. Probably seldom, in fact.
They sound the same, coarse and course. They’re just not spelled the same.
So when you’re writing, you have to know the difference.
How to remember the difference? I hesitate to reveal my personal secret trick: Coarse is two-thirds arse.
See? It’s coarse. Which is why I hesitated to reveal it.
English Is A Complicated Language 