I am fortunate that my office has a large window with a partial view of a tree. The sunshine flows in, although so does the noise. (I do not live in the quietest area.) Still, I can enjoy the breeze and sunlight WHILE I write.
OR, I can opt to go outdoors before my writing time begins. Do my two-mile walk first thing in the morning, or stroll along the seashore (fortunate enough to be a short drive from several beaches.) Then,
2)...you have worries on your mind. Most of us have something to worry about, at times the issues are more worrisome than others. Writing, for me, is a distraction from worry. Of course, the writer needs to LIKE what is being written. If not, maybe it's time to rethink things. Writing in a genre that one despises or is bored with, will not bring joy to the writing, and it'll show. Best to write about what we love to read. What we know best, and/or what we enjoy researching. To approach the computer with dread, is not beneficial to our craft.
3)...you are receiving one rejection after the other, and might be thinking: why bother? This is a tough one to get through. But every writer weathers the storm of rejections, along with the frustration and disappointment that comes with them. Still, we need to forge ahead. Rejections don't mean we are not good writers, it
usually means a change in the publisher's interests, market trends, and even the mood of the editor who reads our proposal on a particular day. If every writer who'd been rejected walked away from writing, we'd not have many a great novel and non-fiction book out there. It's encouraging to read the bio of various famous authors and learn of their struggles toward success.
4)...you're just plain blocked...nothing is coming from your head to your fingers to the screen. Blank! It happens to the best of us. Sigh! Then take a break. Maybe a day off to clear your head. This isn't giving up, it's coming up for air. Big difference. Then when you go back to your project you'll be that much happier and fruitful for the reprieve.