The problem of trying to control temper is one that is frequently presented. It can only be solved slowly under ordinary circumstances. During meditation, he should picture himself in a temper and then deliberately construct an imaginative scene wherein he exercises more and more discipline over himself. These mental pictures when sufficiently repeated and with sufficient intensity will tend to reappear before his mind's eye at the moment when he does actually fall into a temper.
-- Notebooks Category 4: Elementary Meditation > Chapter 4: Meditative Thinking > # 221