The short answer is that you don’t. Doubt will always remain. Sure it has different guises of fear, criticism, insecurity and panic. It is still doubt. Self-doubt is the killer of many a good idea that never got to see the light of day.So what if you are not good enough? Who cares. You are only writing. This is not brain surgery. It is just words. A variation of twenty-six letters typed in a variety of patterns. No one is going to die because of your thoughts, your ideas, or your stories. They will either be interested or not. It is that simple. People will read what you are writing or they won’t.
Some readers will comment, that comment could be either negative or positive. The comment could come from someone close to you or from a stranger you will never see. So what does it really matter?
How many questions of self doubt will keep you bogged down with a head full of wonderful ideas and no outlet. Ideas will die if they do not get to see the light of day. If you as a writer, an artist, a creator fail to give them life they will simply die unattended like a dead mans garden.
So dear friend, do not wait for the absence of self doubt before putting yourself out there. Ride with it. Maybe you are writing crap, but at least you are writing and as every writer knows somewhere amongst the crap something beautiful can grow.