Definition.com
Sorrow is inseparable from joy. It should be remembered, when one is dominant, the other is nearby, asleep.
Definition.com
Sorrow is, along with joy, the only way a person becomes known to himself. It is only through joy and sorrow that one learns what to do and what to avoid.
Definition.com
Sorrow is important to be able to feel. Any mind that is capable of real sorrow is capable of good.