Just to clarify why I think it's important to address shortcomings as well as accomplishments... if you leave out the negatives, it can make your boss think you're just bragging instead of doing a thoughtful self-review.
When I left out negatives, I could tell that my boss spent time thinking about them so the official review would be balanced. It was in my own best interest now to have the boss thinking about the times I screwed up. When I included them, my boss actually downplayed them in the official review. Not to mention it shows people that I will be truthful - the whole truth - even when it doesn't make me look good. That has also helped me in my career.