Yeah, you think as writers we'd be well over that little phobia by now. Nah, it still sneaks in like a cramp from an okay looking piece of fruit that ended up being not quite ripe but we weren't going to waste it and toss it after one bite.
Natalie Goldberg is one of my inspirational writing mentors. I never met her. I have read a number of her books: Writing Down the Bones, Wild Mind, Thunder and Lightning, and Long Quiet Highway several times each. I do that to keep reminding myself that someone else has gone through this, I'm not alone.
Every word is a step. You walk a mile, 5280 feet gives 2112 steps, about 30 inches apart for my stride.
Teams play a football game on TV that lasts 3 hours, but up to that time they have practiced for hours every day 6 days a week for months.
You can run but it took months to learn to crawl, then to walk, and then to decide where to run, for how long, and to what purpose.
Why should writing be any different? Our works don't come full blown like Athena dressed and ready to kick ass--I wish! Words grow, they follow the sun and close up at night. Or they stay still during the day and spread out like night-blooming jasmine. They have a pace and depending on what you feed them--they will keep growing, in unexpected directions sometimes but that's okay too.
Don't be afraid. As Natalie Goldberg says, give yourself permission to write the worst crap in the world.
Even the words you don't use will lead to the ones you do. Call them fertilizer, call them maintenance activities, call them warm-ups for the finale, they aren't wasted.