Having a mission statement for your business is completely optional. However, having a clear and concise statement of why you are in business and what you intend to achieve can speak volumes. It will not only help keep you motivated and on track (like a mantra), it will also give your existing and potential clients a quick snapshot of who you are and what you do. Mission statements reflect the nature of the company they represent.
There is no hard and fast rule or perfect way to create a mission statement (some start off with what the company does, others with company values, and others still with descriptions of the customers the company plans to serve), nor is there a predefined size (some companies opt for very short, even one word, mission statements, while others read like a mini novel). What it boils down to is what will work for your particular business to captivate your audience and keep you inspired and motivated.
If you do create a mission statement, be sure to print it off and have it near your desk to keep you motivated. Post it on your website, the back of your business card, on your promotional materials, and in your advertisements.
Above all, live it!!