Improvement doesn't mean perfection. It doesn't mean you've arrived. It doesn't even mean you're very good. It means you're better than you once were. My high school football team gave out an award for "Most Improved Player" to the person who had shown the biggest improvement from one season to the next. It was a highly respected award because everyone on the team knew how hard that player must have worked.
Improvement is not limited to the football field.
If you're more valuable, you're worth more to an employer or client. In this economy, that's important, don't you think?