Wash face, throw on cozy clothes, drink tea, eat a bowl of fruit, eat a bowl of cereal, start writing.
When tempted to stop, glance out at the blue tits diving across the garden to the feeder, put the radio on, make another cup of tea, drink it while skywatching. But don't get distracted. Write some more. Keep going.
1000 words, 2000 words? Whatever. Enough. Enough for now. Be content. Close the notebook, or save the computer file.
Go and do the next thing, other stuff.
Later in the day, start writing again.
A friend told you what would help in such times - eat a slice of cake!
5006 words so far. That's a whopping chunk of the 50000 word target. Got a bit carried away today. And that piece of cake was SO good!!