The function of mourning in Halakhah is to guide us in properly channeling the natural emotions that accompany tragedy and despair. Indeed, the customs of Tishah Be’av and the kinot are nothing short of ritualized crying. Rather than rise above our emotions, we are commanded to embrace them and let them guide us to teshuvah (repentence). R. Soloveitchik develops this idea in “Avelut Yeshanah and Avelut Hadashah“:
Judaism does not want man to rationalize evil or to theologize it away. It challenges him to defy evil and, in case of defeat, to give vent to his distress. Both rationalizing and theologizing harden the human heart and make it insensitive to disaster. Man, Judaism says, must act like a human being. He must cry, weep, despair, grieve and mourn as if he could change the cosmic laws by exhibiting those emotions. In times of distress and sorrow, these emotions are noble even though they express the human protest against iniquity in nature and also pose an unanswerable question concerning justice in the world. The Book of Job was not written in vain. Judaism does not tolerate hypocrisy and unnatural behavior which is contrary to human sensitivity. Pain results in moaning, sudden fear and shrieking. The encounter with death must precipitate a showing of protest, a bitter complaint, a sense of existential nausea and complete confusion. I want the sufferer to act as a human being, God says. Let him not suppress his humanity in order to please Me. Let him tear his clothes in frustrating anger and stop observing mitzvot because his whole personality is enveloped by dark despair and finds itself in a trance of the senses and of the faculties. Let him cry and shout, for he must act like a human being.