Xi can be translated as elation, le is closer to the contentment aspect
of joy. As a cause of disease most of
the focus in the classics is placed on the deleterious effects of
excess joy, excess xi. It is xi that is described in
Su Wen as making the qi 'loose' (huan), which implies agitation and a
loss of control. Excesses of Joy will lead to disharmony in the body
and cause us to be sick.
There is a well known story in France that when some very old World War
I veterans finally heard that they were to receive a special pension
payment, several died within hours of hearing the news. A Chinese
proverb states, 'When someone meets a joyful event, the jing-shen
flags.' But life is not an endless series of joyful events.