Quandary

How can you be wide awake in the back seat of the car when we are only five blocks away from home laughing, babbling, and waving your arms, and then be sound asleep and snoring by the time I pull in the garage? Then how can you stay asleep and snoring while I take all the groceries into the house, slam the car doors, take your shoes off, take your hat off, unbuckle your carseat, unzip your coat, take you out of your carseat, slam the car door, close the garage door, take your coat off, and carry you upstairs with the sound of the babygate creaking and latching as we go through? How can you stay asleep through all of that and then wake up as soon as I lay you in your crib? Seriously!? Amazing.