Teaching is tough - running helps so much to help u chill out and sort the old brain out.... If u ever doubt that it's doin u good put up 2 pieces of paper on a wall. On one put a tick every time u get back and feel better for going out. On the other put a tick if you don't.... Funny how one stays blank!!! (unless u r unwell, injured or overdoing it!!). Good luck!! - what a story to tell your students (no excuses for them now eh??) - a great inspiration!! Go for it!!