Kids can be like living with a Vulcan. You can have a reasonable explanation for something, but if it isn't linear logic, you'll lose the battle.
Point No. 1:
We're rushing to get to church on Friday night. I shout that the kids should have shoes and socks on and get in the car. My three-year-old looks at me, wearing her white patent dress shoes and no socks, points at my feet, currently shod in black slingbacks (sans socks or hose, of course), and says: "You not wearing socks."
We were late. I wasn't even going to try to explain fashion to a three-year-old. I let her go sans socks.
Point No. 2:
It doesn't matter how many times you tell the eldest that she should leave the easy candy (as in, the candy on the ground) for her younger siblings. If she sees it Easter morning, it is hers.
Point No. 3:
It doesn't matter that you are putting the finishing touches on Easter dinner. If the three-year-old wants to lug her basket around the house and gorge, there's not much you can do that won't result in a screaming tantrum over sugar.
Point No. 4:
It doesn't matter how many bribes, begging lectures, cheers, and discussions you can have about poop with a three-year-old. It will be the weirdest thing that you never thought of that will finally get through her head and result in her being fully potty trained.
In our case, it was the fact that another kid at daycare got an ink stamp for pooping on the potty. Kid 3 wanted one, too. The teacher didn't cave, but told her to go poop, and she'd get one. Boom. That's it. She walks in the bathroom, does her thing, and then continues to do it for the rest of the weekend.
Never in a million years would I have thought an ink stamp on her hand would be the thing that convinced her to do her duty.