When you are in a fluctuating state of mind, like when you are angry or have lost your temper, then it is good to bring back calmness by concentrating on breathing. Just count the breaths, completely forgetting about anger. Concentrate on breathing and count in/out "one, two, three," up to twenty.
At that moment when your mind concentrates fully on breathing, the breath coming and going, the passions subside. Afterwards it is easier to think clearly.
Since all activities, including meditation, depend very much on the force of intention or motivation, it is important that, before you begin to meditate, you cultivate a correct motivation....The correct motivation is the altruistic attitude.
--from Cultivating a Daily Meditation, by Tenzin Gyatso, His Holiness the Dalai Lama