Your brand promise is the 30 words or fewer that define what you offer to whom. If it's not compelling to you, why get up every day and support it? Create a better one and make it real.
Don't confuse the brand promise with the positioning platform, which states how you will present and defend your brand promise against your competition. (Why you?)
One consequence of finalizing your positioning platform might include chasing some of your competitors off the field, and bringing on new ones. Your ideal value proposition lies in competing against the strongest opponents you can find -- the highest price support is on the tougher playing field.