Why mission statements (& SWOTs) are weak instruments

"Unfortunately, you can’t nail down your vision/mission statement (or what I refer to as your Winning Aspiration) without having made your where-to-play/how-to-win (WTP/HTW) choice. Spending time wordsmithing a vision/mission statement before making a WTP/HTW choice is a colossal waste of time."

Check out this short but insightful article: 

http://blogs.hbr.org/2014/05/three-quick-ways-to-improve-your-strategy-making-2/