Do you forget to write what you mean?
When you drive, your main objective is to get from A to B. But when you’re a beginner, you fret the details. There are so many little things to remember… mirrors, gears, gas, and breaks, not to mention the other cars driving around. You’re nervous before you even turn the key. You tentatively back into the road, jerking your breaks when a car passes close by. Then you slow down too much before the intersection, even though there’s no stop sign. When you hit traffic, you’re overwhelmed. You forget your main objective, which is still just to get to B.
Before you get comfortable with all the little actions that make up a short drive, you’ll sweat every single one of them. You might even lose sight of your ultimate destination because you’re so anxious about the intervening steps. You’ll forget, when it comes down to it, that all you need to do is get from A to B without bumping into anything.
The same goes for writing. You’ve got your great idea, i.e. your destination. But you sit down to write and suddenly you’re overwhelmed by the complexity of the situation. “In order to get my point across, I’ve got to write words, then sentences, then paragraphs! I’ve got to use logic, rhetoric, and grammar, too!” If you haven’t been writing much, you’ll sweat. And if, like most, you begin your work at the top of a blank page, the situation can be really terrifying.
Before you begin, make sure you know where you want to go. What are you trying to say? What’s your destination? Keep this in mind as you go along. Take the most direct route, and try not to bump into anything. You’ll be fine.