I recently read this quote about being confident in your work and I couldn’t agree more:  

“There is a difference between being arrogant about yourself as a person and being confident that your work has some value. The first is unattractive, the second is healthy and natural. Some people respond to one as if it were the other. Don’t confuse them. Marketing is not bragging, and touting one’s wares is not evil. The baker in the medieval town square must holler ‘fresh rolls’ if he hopes to feed the townfolk.” — Jeffrey Zeldman.

I think it is crucial that a any business owner be confident in the work or service he or she provides. If you’re not confident in your work, why would any of your potential clients be confident in you? By knowing the value you provide and the expertise you bring to the table, you show that you have a product that is worthy of the price you charge.