Sometimes teachers are in a bad mood before they even get to school. Maybe they got in a fight with their spouse. Maybe they didn't get enough sleep the night before. There are a number of things that may cause stress for teachers before they even walk into the building.
Be on your guard when you know that you are coming to school already in a bad mood. Don't let it affect the way that you treat your students.
When you feel like you are already in a bad mood before the school day begins, recognize it and don't let your emotions get in the way of treating your students fairly. Do whatever you can to be as unemotional as possible when handling discipline in the classroom.
Working with children is not always an easy thing to do, especially when you are already in a bad mood. Knowing ahead of time that your bad mood may cause you to treat your students unfairly can help you prevent it.