One of the most compelling things I've learned from watching Chef Gordon Ramsay's "Kitchen Nightmares" is to not send sub par food out of the kitchen. But when is a work of art good enough? Sometimes not sending work out means a missed opportunity. Sometimes showing work too soon invites overwhelming criticism. Sometimes quality is just a matter of opinion.
Seek out the opinions of those who you respect and then listen to their comments without interrupting. Write them down. Often revision suggestions will seem much more positive once the sting of not being completely perfect and wonderful has worn off. If the comments seem off the mark, your work may need more clarity. Sometimes I just haven't yet learned something I need to know for a particular project. Neil Gaiman put off writing "The Graveyard Book" because when he came up with the idea, he felt that he was not yet a good enough writer for that idea.
The critique group I belong to is invaluable and far more expedient for feedback than putting work in a drawer to be looked at months later with fresh eyes. We let each other know ways to improve our work, and when it is good enough to send out of the kitchen.