Set goals. Last year, I promised myself that I’d write a poem per week. At the end of 2017, I had 48 poems. 48 more than the previous year…
Care less. Get the idea written. Worry about quality later. To paraphrase Neil Gaiman, you can fix it at another time.
Automatic writing. Drink a reasonable amount of red wine. Fetch your preferred instrument of writing, and write. It worked for the Surrealists.
Time limits. You have ten minutes. Procrastinate for nine minutes. Panic for the last 60 seconds and scrawl something. You now have more writing than you had before.