In order to define success you must first define the direction and aim of your efforts.
To define your mission statement, follow these series of steps.
First, pick a STAR. The STAR should be something that is very hard, almost impossible to reach but is still possible. For example, Coca Cola's is "to serve every ounce of consumable liquid."
Once you have picked your STAR, identify your CORE MOTIVATOR. This is a verb ending in -ing that best captures why you do what it is you do (your brand, not necessarily yourself but the two may be synonymous). If you have trouble identifying your CORE MOTIVATOR, write a one page history of your life and we will talk about it in class next day to look for clues as to your CORE MOTIVATOR.
With these two core pieces, the last step is to identify a series of MOUNTAINS that you will climb in your lifetime (or during the course of your strategy), each bringing you closer to your STAR. The best way to define these is to work backwards, starting with a long-term MOUNTAIN (10+ years in the future), then a mid-term MOUNTAIN (5 years) and finally one for the short-term (next year, after your initial strategy has been complete).
Finally, put all of these things into a single paragraph of 4-5 sentences and that is your mission statement.