If today were the last day of my life, would I want to do what I am about to do today? And whenever the answer has been "No" for too many days in a row, I know I need to change something - Steve Jobs (wow.wish I could live by this)
"If the plan doesn't work, change the plan but never the goal." Sometimes I do this in the midst of a lesson plan! The fact that my day can be so well-planned and then so unpredictable is one of may favorite parts of the job.