As anyone who has attempted to keep a 200+ dwarf fortress running for any length of time, it becomes scarily apparent that the Mountainhomes must risk cataclysmic depopulation every season or so from some tantruming or berzerk dwarf going on a rampage and setting up a deadly tantrum spiral. So how does any dwarven civ last more than a few years in world gen if they're set up to self-annihilate so often?
Tantruming dwarves should become a dwarf who is increasing their military skills in a non-lethal manner by slugging someone else, but instead creating bad thoughts or a grudge with whomever they attack. The emphasis here is "non-lethal", however. A mother who hears her uncle was killed by a goblin doesn't immediately throttle her bouncy baby boy then proceed to go on a lethal rampage because her baby is dead - that's just stupid from a biological survival standpoint alone. No, instead, she yells, screams, kicks the walls, (or maybe she goes to the craft-shop and commissions a job to carve a memorial to her uncle? Why should the overseer have to decide that for her? maybe the Overseer just has veto power over the uncle getting a memorial?) Anyway, her antics keep nearby dwarves from sleeping well which might form some grudges, but eventually life goes on and here's the kicker: Nobody else gets slaughtered just because one dwarf decides they're upset about something.
What I'd like to know is why the greatest threat to dwarves isn't an invasion by evil goblins, but the resulting tantrum spirals that happen after one is repulsed. SO MANY TIMES I've had 1-2 dwarves lost to invaders and 30-50 dwarves (sometimes even 100+) lost due to someone mad about those 1-2 dwarves dying. It's crazy, and idiotic for dwarves to want to live together if by doing so, they have a greater chance of dying due to random bad moods.