Try Squibler, the Most Dangerous Writing App, which shuts down and abandons your progress if you stop writing for more than a few seconds. Just set a target number of minutes, generate a prompt or start without one, then make sure to keep tapping those keys. There’s nothing more motivating than the threat of annihilation.
This tip is from 19 Tricks to Shatter Writer’s Block. If you missed any of the previous tips, you can find them all in the Hack Your Noodle section of Read Write Repeat.