Like - one of the dwarfs went insane, cause you forgot to give him proper bed, and when he wanted to make some artifact there were no forge available for a long time.
Then he goes berserk and kills a few other dwarves. Your police force kills him, but your cemetary is full, so a few bodies were left by dwarves to rot in the cave (you shoud have checked that, but you were busy on the other level ensuring dwarves have something to eat).
After a few weeks miasma from the bodies is everywhere, and other dwarves went insane from it, killing each other. A few still sane try to stop that, you try to divide caves with doors to stop the miasma and insane dwarves, but then the sane one die or go insane from starvation. Or because their friends or partners were killed. And then goblins come :)
That's how most of the games look, but thanks to insane level of details it's much more varied. Sometimes it's flood that takes your fortress, sometimes it's lack of water, sometimes it's digging too dip and revealing subterran horrors.
The game has steep learning curve, but it's very rewarding.
Not for nothing is the community devoted to megaprojects. Not only are they cool they offer countless ways to introduce Fun into your boring, dreary existence. And sometimes they even work; the "minecart shotgun loaded with gold bars (because, why not?) complete with optional F.R.O.G.G.E.R. system is just a gorgeous thing to watch happen, and it's viscerally satisfying to watch some goblin take a gold bar going a good 30, 40 mph to the face.