It's easy to keep working on the thing and to slowly move it in the direction of "perfect." It's hard to have a set time after which the thing is done. It's hard to put hard work out there for others to look at, judge, and whatever else they feel like doing at the moment.
Make something and get it out to the world. Ship it. The fear will always be there, but not shipping is worse than any criticism.
Act with courage. Move forward. Ship it.
Note: if you don't know who Seth Godin is then you're missing out.