Just smile

Smile even when you don't feel like it (and a parent is calling you bad names).

Smile at the children (even when they have attitude issues and want to fight).

Smile at the teachers (even when they are angry about a small issue out of your control).

Smile at the beginning of the day (even when a bus driver has a dead battery).

Smile at the end of the day (even when your boss calls you to tell you about a complaining parent).

Just smile.