What is the difference between mourning and sadness? Mourning takes hold of one’s heart, but not one’s mind, while sadness takes hold of the mind. Mourning leads to thinking, while sadness stops one’s thoughts. Mourning stems from the light in one’s soul, while sadness comes from the darkness of the soul. Mourning arouses one to life, while sadness brings to the opposite. The Torah obligates mourning when it is appropriate, while it forbids sadness and commands we serve the Almighty with joy.
When we pray, we should feel the seriousness of speaking directly to the Almighty. The concept of seriousness should not be mistaken for sadness since sadness is a transgression. Seriousness should stem from the true joy of fulfilling a mitzvah [biblical law or good deed], the joy of having the merit to pray to the Almighty.
By sadness you destroy the divine image in your soul. God is joy. All nature rejoices in him, and would you be sad? A true joy makes the heart fear God.
"Keep aloof from sadness," says an Icelandic writer, "for sadness is a sickness of the soul." Life has, indeed, many ills, but the mind that views every object in its most cheering aspect, and every doubtful dispensation as replete with latent good, bears within itself a powerful and perpetual antidote. The gloomy soul aggravates misfortune, while a cheerful smile often dispels those mists that portend a storm.
Atheism leads not to badness but only to an incurable sadness and loneliness.
What is God-given is called nature; to follow nature is called Tao (the Way); to cultivate the way is called culture. Before joy, anger, sadness and happiness are expressed, they are called the inner self; when they are expressed to the proper degree, they are called harmony. The inner self is the correct foundation of the world, and the harmony is the illustrious Way. When a man has achieved the inner self and harmony, the heaven and earth are orderly and the myriad of things are nourished and grow thereby.