I will admit to being a hair-trigger abandoner.
I'm glad I finally broke that habit last night with my first true fortress death.
Breached caverns, sealed caverns back up. Dug out fort, got industry going. Discovered need for building walls. Discovered shiny vein of cobalt; usless for metalworking, but very pretty when turned into blocks and made into wall sections. Start expanding my vein...end up breaching another set of caverns. Put a wider seal on it so I could get at a big patch of the cobalt in the cavern proper. I must not have sealed it up properly.
A trio of Molemarions run into my fort and proceed to murder everyone horribly. I manage to kill ONE with my cobbled together military (I had no formally traided military yet, still the first year). The other two cut me down to 4 dwarves by the time the caravans arrive. The guards dispatch the wounded Molemarions.
Define a makeshift hospital (I don't have any equipment for it though) two of my dwarves are crippled and brought down there. One is badly wounded and my miner is the only healthy one of the bunch. Miner delivers food to the two cripples.
Miner then has a bearserk tantrum and murders the two cripples with his bronze pick, slaughters his way through my livestock and even gouges both legs off one of the cavern guards before the other guards take him down.
Final dwarf has "Her head is dented" as a wound, but she's still moving slowly. She shambles her way into her bedroom and goes to sleep. Seeing the 'unconcious' status, (rather than the sleeping) I see she's slipped into a coma. With nobody to feed her, she dies of hunger and my fort crumbles JUST as 2nd spring arrives... all for some shiny blue cobalt rocks to make pretty walls with.
In other words, a proper dwarven fort death.