Developing a mission statement for a business is an interesting process.
Firstly, it usually means that you have chosen some kind of vision for your business (the why / what question). Secondly, it usually means that you have some idea of how you want to realise the vision (the how).
'Mission Drift' is a term I heard a number of years ago and I think it is a good term to apply to our continuous improvement activities.
If your business started to behave in a way that wasn't congruent with your values then you wouldn't achieve your vision. If your business started to work toward objectives that don't fall in line with your mission statement then you probably wouldn't end up where you wanted to be.
Mission drift is when we fall away from what we were meant to be doing and do something else.
In your business your continuous improvement activities will hopefully align with your vision and mission statements.
If they don't then it might be time to review how you spend your time and which projects are important to the business.
Author of 'Business Process Re-Engineering', a practical plan to improve business performance.