To be calm or not...

Hypertension patients are known for short tempers. But there is a paradox. A person who is outwardly very calm, may also be suffering from high Blood Pressure, as his outward calm may be a façade of his inner turbulence. He does not blow up, but keeps everything with himself thus building up the pressure. So is calmness good or bad? I would say such kind of calmness is good for others, but bad for the person himself and blowing up is bad for others and good for self. So, is it better to be self-centred?