It's entirely OK to sit and write without fanfare, we're not wizards or witches any longer, just plain people with the same plain obligation towards the mind as towards the body: tend, feed, and regularly empty out.
If today you really gotta go write, go ahead, knock yourself out.
If tomorrow you just scribble in the margins of empty pages but nothing comes, have a bath or a nap or both, and sit again the day after.
I also find it very helpful to remember that I'm not addressing others when writing, I'm not in a possibly empty auditorium talking into the void, instead I'm reaching across time and continue a discussion I started with myself earlier, and may pick up again later.
The trend since stationary became affordable has been to get a daily journal going, and start some weekly correspondence, that'll give you opportunity both to write and to communicate, and you'll also creating a self-referential echo chamber, and you bootstrap yourself up from there.
It helps a lot if you have questions that bug or interest you. Writing is thinking, you have to want to think about something, don't confuse it with presenting the writing.
Writing helps you sail on the void and dive in its depths. An audience isn't necessary for that, so if you get your writing done on the computer rather than on paper, remember that you don't need to publish it. That may take a load off you, and free you to think about what you want to write, not how it'll be typeset or who will read it or whether it'll get points, stars, or otherwise pointless superficial kudos.
In fact, write daily, but don't publish until after the first couple of times you burn your past notebooks (or "rm -rf ~/txt", though its really not the same).
PS, I just got this stuck in my mind, if you need a silly essay prompt: If you don't write when you think, how do you know that you're thinking when you think you're thinking, rather than hallucinating thinking that you're thinking?