Well I've learned that when it comes to relationships, each individual has a threshold for how much "word" tolerance they can accept before they engage in "time to bite ass" mode. They store those unsavory moments of hurt feelings to preserve the relationship at first, knowing that its a necessary sacrifice in order to get to know a person better. But once they have had enough, they can no longer tolerate those little moments of sarcasm and must defend themselves by fighting back. To the individual on the receiving end of this, its a great wtf blindsided moment. It's like the limit break from final fantasy 7 where your character takes small bits of damage over time to fill up the gauge and then unleashes their strongest attack. Lulzz