Try music. There's something about the way that the human brain juggles its processes that makes listening to music help people focus. Nothing with lyrics, mind you, or at least lyrics that you can understand. If you are paying attention to lyrics, then the part of your brain that is responsible with processing language will be distracted from putting words to paper. (Or words to a screen, or whatever you're using.) Try classical music, or perhaps background music from video games. You can find video game music posted on YouTube in loops that are hours long. And no rap. Rap doesn't have a melody so your brain does not get engaged in the same way and it is too dependent on lyrics.

If that doesn't work, then disconnect your internet connection to prevent distractions and just hunker down and get to it.