Most of my writing sucks. And that fact actually helps me.
It's yet another of the awful ironies of writing: being convinced that most of my writing is horrible actually helps keep me from putting substandard material in front of readers. It causes me to rework my writing repeatedly. It drives me to edit it more. It forces me to take extra steps to make sure that I protect my readers from my crap. It helps me improve.
Like I said, most of my writing sucks. But I make damn sure to keep that writing out of the public eye by reworking it and reworking it until it doesn't suck.
My insecurity about my writing helps me be a better writer. What about you?