Rabbi Steinsaltz writes:
Sadness is a great obstacle to the worship of God, and man must struggle against it as much as he can.
Even though there is a passage in the Bible that states: “In all sadness, there would be profit …. ” (Proverbs 14:23), which may appear to be a contradiction.
Of course, the meaning is not that sadness in itself can ever be profitable, but that there is a joy that often follows on sadness, which, thus, may be good.
For there is also the matter of catharsis or purification, as well as the fact that there is a time for everything.
Sadness can, therefore, be a vehicle for attaining something else, a bitter remedy for a worse ailment.
On the other hand, life furnishes enough genuine reasons for being downcast.
Thus in order to prevent sadness from being a dominant factor in life, we appoint special times for it–such as fast days or days of penitential prayer–and banish it from the rest of our lives.
Nevertheless, there is sometimes a real need for a contrite heart.
Because the greatest hindrance to spiritual awakening is a certain smugness, a dullness of the heart and mind.
In this case, all the books and all the messages of spiritual love will not avail.
Indeed, self-complacency is a more serious obstacle than depression or stupidity.
To overcome it, to smash through the barrier of “fatness” of soul, it is often necessary to pass through some sort of crisis or tragic experience.
And this is often brought about by heavenly intervention, against one’s own wishes and designs.
–Rabbi Adin Steinsaltz