"For one who has conquered the self by the Self, the Self is a friend; but for one who has not, the Self remains as an enemy in hostility."
Modern explanation
In the middle of the day, return to this: When you cannot master yourself, you become the person you most have to defend yourself against.
Practical application
Before responding to the thing irritating you, draft your reply, wait ten minutes, then re-read it.
Reflection question
What boundary is this anger asking me to set, calmly?