When I was 8, I started pulling my hair—specifically the hair at the very edge of my hairline. Now, I was blessed with a thick ol' mane, so the effect of the hair-pulling wasn't visible.
Weeks went by. Every day, I twisted up a few hairs at a time, rolling them between my index finger and thumb. Then I'd rip it all out. I didn't know what a "compulsion" was then, or even knew the words "anxiety response." I just kept doing it because I felt like doing it.
Then one morning, I pulled my hair back and saw it: a massive bald spot where my widow's peak had once been. I'd pulled out my entire hairline, and pretty soon it was going to be impossible to hide. Days later, my mom (to her horror) saw what I'd done.
My mom opted to shave my head to give my hair a chance to grow back evenly. It did, and I eventually abandoned the compulsion. What I walked away with was a material education in the power of small actions on a daily basis: a few ripped hairs here and there was impossible to notice, but a few ripped hairs every day was impossible to ignore.
The upside is that I internalized that lesson in a constructive direction: writing.
The power of consistent action
The primary aim of a daily writing practice isn't output, but consistency. That means your metric for success isn't how many words you've written on a given day, but how many days in a given period that you wrote anything at all.
So make consistency easier: set a low daily word count goal.
Over time, you'll naturally grow your word count beyond your baseline, but even if you don't, your overall output will explode. 300 words a day for a year is a novel (and I don't doubt that you'll write way more than 300 words on most days). A few words on one day is impossible to notice, but a few words every day is impossible to ignore.