You have to ask yourself, how far are you willing to go to keep your one daughter from eating the other daughter's cheerios? And how will you prevent your ten month old from pulling a giant potted plant onto her head? What about keeping track of your three year old and your ten month old while you take 70 seconds to pee? Is that really enough time to get all the way into the kitchen while crawling and pull a glass bowl off the second shelf onto the hardwood floor (no, it didn't break). And what does scary monster, scary monster really mean - is that actually an indication that your older daughter has covered your younger daughter with a giant laundry basket???
As Mitch says, you try to be the shepherd. But some days you aren't even the sheep. In fact you're not even the grass the sheep is eating but would be more accurately described as the fine dust that the sheep have walked on for centuries, grinding it down until a slight breeze can blow it away.
Which isn't to say that parenting doesn't have its upside. I'm just saying, its not for wusses.