Seminary students have a LOT of writing to do. This article has some great counsel on honing your ability to write.
4. Give yourself time. Many smart people tell themselves pathetic lies like, “I do my best work at the last minute.” Look: It’s not true. No one works better under pressure. Sure, you are a smart person. But if you are writing about a profound problem, why would you think that you can make an important contribution off the top of your head in the middle of the night just before the conference?
Writers sit at their desks for hours, wrestling with ideas. They ask questions, talk with other smart people over drinks or dinner, go on long walks. And then write a whole bunch more. Don’t worry that what you write is not very good and isn’t immediately usable. You get ideas when you write; you don’t just write down ideas.