Rough Drafts

One of the hardest lessons in writing, at least for this author, was the concept of the rough draft. Being a detail orientated person means that getting it right the first time is incredibly important. But in real life writing it isn't. Things change and the story has too as well. It can be painful when the teacher forces you to sit down and pour out your ideas in an ungrammatical mess in a brief 15 minuets and then cut it up and do it all over again and again. But the results can't be argued with. 
What was one of the hardest lessons in writing for you?