First, always hire a kid to do it. It's cheaper and easier than hiring someone else or doing it yourself.
Second, if the kid goes out of town, do it yourself. The first week.
Third, if you didn't mow it yourself the first, second, or third week, don't expect to be able to mow it easily.
Fourth, if you are going to have to mow it yourself and you didn't mow it until it was knee high, borrow a self-propelled lawn mower.
Fifth, whether you borrowed a self-propelled or not (I didn't) do it early in the morning. (Finally, something I did right.)
Sixth, when you're doing it, if it gets to be too much, stop. Don't keep mowing till you collapse on the grass. (I made it inside the front door. The neighbors were out and I didn't want to be embarrassed.)
Seventh, if you keep mowing till you're past sick, do have good kids in the house who will bring you water from the fridge, your pillow, and a cool wet cloth.
Eighth, if you don't finish it the first day, it's okay. You can do a bit every day and not make yourself sick.