Have you ever turned around and looked at your middle schooler or high schooler and thought: "Who are you? And what have you done with my child?"

That loss of your child to this thing called adolescence is what Austin psychologist Carl Pickhardt writes about in his newest book, "Who Stole My Child? Parenting Through the Four Stages of Adolescence" ($17.95, Central Recovery Press).

"Adolescence begins with loss," he says. "They are never going to have their child again."

That can be very difficult for some parents.

"One of the issues that a lot of parents have is they are in somewhat of denial that adolescence is going to happen, and when it happens they're not sure what to expect," he says.

Parents also don't realize how long adolescence lasts. In the book, Pickhardt outlines four different stages, going from age 8 to age 23.

Pickhardt's intention with this book is to give parents a road map so they can know what to expect before it happens.

It's important to note, Pickhardt says, that parents don't need to fear adolescence. About one-third of kids go through adolescence "without much of a ripple," he says. Another third will have some bumps, and the last third will get stuck and need to come into counseling to get back on course, he says.

It's not all bad, he says. It's actually a magical coming-of-age story, he says. You get to see a child become an adult.

Yes, the relationship between you and your child does change, and you want it to. The ultimate goal is that, hopefully, by 18 to 23, they have practiced enough self-management to be independent. "That's what needs to happen," Pickhardt says.

Between ages 8 and 18 is this period of kids detaching from parents and their previous childhood self and pushing for more independence. They are experimenting with individuality, he says.

That sometimes shows up as kids trying to change their personalities and finding completely different friends. Kids who were shy in middle school might suddenly decide to try out being extroverts in high school.

It also shows up as those kids who were affectionate toward their parents suddenly not wanting to be hugged and becoming happy to practice eye-rolling. That kid who told you everything no longer tells you anything.

"You can't really hold the kids back," he says. "These changes will happen."

It takes courage for parents to let go, he says. And with children, "it's really important to remember adolescence is an act of courage. It takes bravery to try yourself out in new and different ways."

Of all the stages of adolescence, Pickhardt says, the last stage, between ages 18 to 23, is the most difficult.

You have to let go, but sometimes they aren't ready for that. This is the age when kids can start floundering. "They lose their footing, and they can boomerang home," he says.

What can parents do? They should create a family structure with rules and expectations, he says. They then should hold their kids responsible for their choices and the consequences that follow.

"A lot of adolescence is mistake-based education," he says.

Where kids get in trouble is when they don't take the time to stop and think about what decision they are going to make. Parents, he says, should encourage kids by telling them, "Before you make one of these decisions, stop and ask yourselves some questions: Why do I want to do this? Are the risks worth the reward? If this goes badly, what's my backup plan?"

Even good parents have good kids who sometimes make bad decisions, and even good parents make big mistakes too, he says — but rest assured, your kids "are going to come out fine. They are going to grow up fine in part because of what you did, and despite what you did."

In addition to getting to watch your child grow into an adult, the "sweet stuff," as Pickhardt calls it, is when your child, the now-adult, starts appreciating you and coming to you for advice.

"Parent's didn't know anything, then at the end of adolescence, they know a whole lot," he says.

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