This question/statement, "I don't know how you do it!" comes from The Stone Age Techie. Thanks for the memory jog, Karen! Her answer was great too:
"I don't know how I fought with him for hours each night to finish his (first grade!) homework, or how I hauled him out of bed, shoveled food down his gullet, and got him out the door each day for school... we are all so much happier without that in our lives anymore!"Since I never experienced the joy of waking up my children before 8:00, I usually give a somewhat simpler response to this question.
The partner statement for "I don't know how you do it!" is usually "I could never do that!" I hear that a lot. I never did figure out a clever response that one. Any takers?