"Behold, I set before you this day a blessing and a curse" (Devarim11:26) In the Hebrew there is a contradiction withing this verse. The Hebrew word for "behold" - the name of this portion - re'eh (literally, see) is directed to the individual, while the the Hebrew for "before you" - lifneichem is in plural, before the entire Jewish communal entity. The idea here - as teased out by the Kotzker Rebbe is that while the choices of blessings and curses are put before everyone, each unique individual perceives these realities in divergent ways. Nevertheless, everyone has the chance to make truly healthy choices.
Rabbi Bernard Weinberger in his sefer Shemen Hatov on 14:1 first addresses what he considers to be the simple meaning of the flow of these words: "You are the children of the L-rd your Go-d, you shall not cut yourselves, nor make any baldness between your eyes for the dead." Because you are children to G-d therefore you should not react by cutting yourselves when a dear one dies. A prince is exiled into the army and a time comes when he leaves the forces and goes on to be king, A soul is sent to learn things in this world and eventually returns to G-d. The soldiers, the relatives, need to not despair because the beloved is returning to where he belongs.
Yevamot 13b teaches that lo titgodedu, besides its literal meaning of not mutilating oneself also means "lo taasu gedudim"- don't break away from the community into clusters. The Shemen HaTov addresses how this ruling is derived from the verse although the literal context and the homiletical explanation seem unrelated. He suggests that nothing brings out individuality like the loss of a loved one. Everyone mourns in their own fashion, accentuating a different element of the loss of this life. The fact that everyone reacts differently to a loved one's death can lead to families breaking apart in the wake of that loss. It is specifically in light of death which can exacerbate divisiveness that we are implored to stick together.
This relates to Yirmiyahu's cry, "Habitu u're'u im yeish mach'ovkemach'ovi" (Eichah 1:12) - "Look and see if there is a pain like the pain I am experiencing." The Maggid of Dubno keys in on the wordmach'ovi.. He tells the tale of a palace built and burned to ashes. Some cry over the loss of the home they lived in, others over specific furniture or decorations. The owner is the only one who knows that he had hidden treasures in that house, so he cries harder and in a different way than anyone else. Yirmiyahu knew the deep meaning of the BeitHaMikdash, a meaning lost on the masses. He tells them that they can't get the tragedy in the way he does, their mourning and his mourning are quite different.