Whine

I used to wonder why parents gave in to badly behaved children.  I worked with kids, so I knew these parents were shooting themselves in the gut.  Show any sign of weakness and kids are on you like jackals.  Or, put more dispassionately, if you reinforce a behavior, you get a whole lot more of it.  

Now I understand.  It's a dose issue.  Eight hours of kid a day is one thing; 24 hours of kid is... three times that thing.  You have the potential to get ground down.  Add in exhaustion and distraction, water heater explosions and poop, and sometimes you crumble.

I'm still pretty good about not rewarding bad behavior, but my empathy has broadened; never a bad thing.