hold one's temper

Idioms  

1. Also, keep one's temper. Refrain from expressing violent anger, maintain composure or poise. For example, Billy has to learn to hold his temper when he's frustrated, or If the chairman can keep his temper, the matter will get settled. [c. 1700] For an antonym, see lose one's temper.

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Example Sentences

It isn’t so difficult to hold one’s temper while sitting.”

From Captain Pott's Minister by Cooper, Francis L. (Francis Le Roy)