Many resources correctly recommend good lesson plans, making a presence in the room, or other things as key issues to good teaching.

However, the most important factor is a good night's sleep.

This factor is so important that you can come to class with a bad lesson plan - or no lesson plan at all - and manage, if you're rested. The lesson won't be great, but you will be able to manage the class, exert reasonable discipline, and teach to some degree.

If the situation is reversed, and if you have a very good lesson plan but you're tired, you will flop.

Discipline in your class will be poor when you are not rested. Sure, you'll blame the kids but they are not fully to blame.

When you're rested you're more interesting, the lesson flows more smoothly, you cover things in more rapid fire order, and you can control the class. You can also explain things, issues, and concepts more successfully when you are rested.

When you're tired, your brain is also tired.

Thus, all the other guidelines and rules are valid and important. Do them.

But they will work only if you are rested.

Let's take the following situation:

It's late at night. You haven't prepared your class yet. You're tired. What should you do?

The answer is to go to sleep. That will give you a chance of succeeding the next day. If you opt for preparing the lesson, no matter how good it is - you'll be even more tired and you will not be able to succeed the next day.

Of course you can't do this too often. You should prepare the lessons for every class and be rested.

However, the world is not ideal and sometimes it's impossible to get all of the sleep that we would like. This offers you an option of how to survive in an imperfect world.

This is also closely related to sleep.