First of all, Hi! New Dwarf Fortress player here.
Now onto my rant. Goblin Invasion: I don't feel like dealing with it. My fortress is guarded with a drawbridge, so I decide to use that to ignore the invasion with. I only have a few dwarves outside gathering wood, so I undesignate the trees, and wait until the last of them returns. The invaders are still milling around the edge of the map. I designate the lever to be pulled. And I wait. And I wait. And I wait. The goblins are starting to get close, so I station some speardwarves well within my entrance in case any goblins get through the traps before the bridge goes up.
Goblins mill around the entrance. Then what to my speardwarves decide to do? They decide to abandon their post, cross the bridge, and attack the goblins. There is still no dwarf even thinking about pulling that lever, even though I have multiple dwarves standing around doing nothing. My speardwarves push back the initial goblin force, but they don't move back inside. No, they are wounded. And now my other dwarves are moving to recover them. Now the goblin bowmen are shooting at the civilians gone to collect their wounded. My dwarfs are dying, and now more of them are going out to collect the possessions of the fallen. I've already lost the master engraver who should have been no where near the action.
I say **** it. I'll send my whole military out to deal with the goblins. Now that my fighters are crossing that drawbridge to fight what happens? A helpful administrator retracts the bridge.