This does not mean you have to explode every time. The happy mean is a healthy sign, showing you have the capacity to be tolerant. A spontaneous smile at a passing neighbour or child, or at reading a comic strip are all indicative of good health. A healthy man or woman is a person who accepts the truth portrayed. A hypercritical attitude is indicative of continuous conflict within oneself.
Happiness is what health is about.
All healthy people have that innate capacity to rise above to that state of consciousness whereby you are filled with love and compassion towards all creation. A positive attitude can be a potent weapon against serious illness.