First of all, no one talks about having kids or teens, it's about babies. Guess what? Babies are easy. And ridiculously temporary. Have all the babies you want, but know that they turn into something else entirely and then you're dealing with this:
{1}Your house will NEVER be clean again. Ever. It seems like a small price to pay for a cute little family, doesn't it? Sure, but if you pride yourself on a clean home, you better look for another source of pride. Or a cleaning lady and a daycare that keeps your kids out of your house seven days per week.
{2}You will NEVER sleep again. Having a kid up at 5am or awake until 10pm is not unusual. Hopefully you only have one or the other. And age doesn't effect this; in fact, babies sleep BETTER than kids. You will begin to define a good night's sleep as just having one kid in your bed and only waking up three times for various ailments, bad dreams, accidents, etc. And that's after they've gotten up seven times before even falling asleep for water, to complain that someone's being too loud {oh, the irony}, or to ask what we're doing tomorrow.
{3}You will ALWAYS be dealing with food. It's a constant stream of packing lunches/snacks, listening to complaints about how disgusting/too cold/too hot/can I have chocolate milk instead?/that's not how so-and-so makes it, and cleaning up. And don't tell me to just have the kids clean up. Mine do. Have you seen how kids clean? Have you seen how husbands clean? It's about the same. So you're STILL cleaning up after clean up. And yet, it's never clean {see #1}.
{4}You will NEVER see an empty laundry basket. Self explanatory.
{5}You will NEVER be alone. And out of desperation, you'll start inventing ways to be alone: arriving an hour early for doctor's appointments, purposefully waking up at 4:30am just to enjoy a cup of coffee, or going back to work.
If you have a baby or are thinking about having babies, I'm sure you're shaking your head and mumbling, I would never let my life become like that. That's ok, I said the same thing. It's self-preservation. No one wants to think that a little teeny tiny baby will turn their lives into a disheveled, chaotic mess. Don't worry - babies don't. It's those dang kids.