Yeah, I've been struggling with the same stress problems with certain dwarves. Some dwarves just are a bit mental! My notes on trying to chill out various of my dwarves
* Above 250k is where you'll get tantrums, and you really need to act before it gets to this point because once it's gone beyond this, it's really hard to get back down - they start getting annoyed that they've just started some fights and thrown tantrums.
* The worst problem seems to be seeing old body parts. Some dwarves just really really don't like this.
* The corollorary to this seems to be some dwarves that just go mega-happy regardless.
My solutions so far are:
* Put a wall around your refuse stockpile. Atom smash any and all corpses that aren't destined for the butcher's shop on a regular basis.
* Any "stressed" dwarf (100k+) is removed at least temporarily from the military and has refuse hauling labour turned off.
* In extreme situations, have a "chill out" zone. This is an area with 4 rooms - a dormitory, a statue room, a food / booze stockpile and a dining room. The area can be sealed with a bridge. Put the stressed dwarf(s) in a military squad (with no uniform!!), station them in the chill-out zone then pull the lever to seal them off and put them off-duty or remove them from the squad entirely and unset all labours. With time, their stress levels will plunge - "Sulky Asmel" was at 255k stress and is now down at 170k stress after being sealed in for a year now. He occasionally grumbles about not having a shoulder to cry on, but stress is relentlessly dropping.
** I'm planning a further experiment where I sequester 10+ dwarves in a chill out zone with a barracks/archery range/etc, plus a few potential pets. Hopefully they'll get positive thoughts from making friends / satisfying sparring sessions, etc. as well. I shall report back when experiment is done!