Share it with other people. Present your autobiography to your reading club or a friend so you can get an outside opinion. Stories you find impossibly funny might seem dull to someone else. Get feedback from several people if you can, so you'll have a better idea of how your book comes across to other people.
If several people recommend cutting a certain section, strongly consider making the cut.
Try to get opinions from people outside your circle of family and friends. People who know you might try to spare your feelings, or they might be biased - especially if they appear in the story.