A blank page intimidates people. Time and again as a writing tutor working in Boston I have had the following experience: I meet a student, I read their paper, and I come across an unclear passage.
When I point out that the passage is unclear and ask them what they were trying to say, they look up from the paper and speak directly and fluidly to me in remarkably clear explanatory phrases, phrases that are much more vivid, direct, and informative than what they have in their document.
Then, when I ask them to go back and write that down, they shift their attention back to the paper and they immediately freeze up. Their shoulders hunch, their brows knit, and they start struggling to find words. They are weighted down with the assumption that writing has to be a much more formal, stiff, and alienating experience than simply communicating to another person.
So they hunt around for fancy words; they struggle to make their clauses and phrases more complex; they use words and phrases they would never use in conversation. This makes it harder for them to write, and it even makes it hard for them to think through what they want to say, since they think in their "writing voice".
In one sense, they're right: a written paper shouldn't look exactly like a transcript of a conversation. But this doesn't mean that writing is essentially any different from the basic process of communicating to another person. It's just another form of it.
If you think that when you write you need to shift from communication-mode to writing-mode you will wind up with stiff, stilted writing and unclear expressions; expressions that cost you a lot of effort to come up with anyway. So next time you are writing and find yourself struggling or stuck, close your laptop or look away from your computer. Stop trying to "write". Forget about the page completely. Just imagine yourself talking to someone you know, or find an actual person; a friend or a writing tutor.
Think about using this study skills. Imagine yourself responding to their casual question: "So what's this part of the paper about?" Then explain it to them, informally and casually. Don't worry about phrasing it well or anything. Just worry about helping your friend get a handle on what you mean to say.
If it helps, imagine you're doing this so that they can write the sentence for you once you have explained it to them. You might even consider recording yourself. When you're done, look back over what you said, or have your friend repeat your exact words back to you.
Generally, what will happen is that the phrases you used to explain the issue to them can be put directly into your paper, and they will be very well written. There won't even be a need for them to write the paper for you (which they can't do anyway!). Even if the phrases you used can't be put directly into the paper, it will still give you a better idea of what exactly you want to say, and will make it easier to write.