If you shovel your driveway when the snow is fresh, the snow usually comes up easily, leaving clear pavement.
If one car drives on it, you’re left with deeply compressed tracks that are near-impossible to clear.
Before you express anger to your students, before your temper gets the better of you, remember: expressing anger in class is driving a car over fresh snow. Once you’ve done it, you’ll never get back the pristine, open spirits you had before.
It might be necessary, on occasion. But then again, with planning, it might not be.