He has great self-restraint and never loses his temper.
Tips
usage
能控制情绪的功夫 - 'the skill of controlling one's emotions'. 涵养 is the dignified composure that survives provocation. Often paired with 有 (有涵养 = 'has cultivation').
memory
涵 = 'to contain water'; 养 = 'to nurture'. Picture a deep reservoir that absorbs storms without overflowing - that's 涵养.
