Preparing is fine, but worrying about tomorrow isn't worth three seconds of today. It will come when it's there and ready and no sooner and no later. As a teacher I know about planning and I do my share of planning. But as soon as that plan is written up it is forgotten until the next day. Out of sight it is out of mind. I have a few notes stashed away at the end of the day but that's it. I am free.