In the always-complex, often-painful world of family caregiving, there is no worse advice than this: When your parents need help, you must reverse roles and become their parents.

Here is the reality: If you are the adult child of an aging parent, you will always be their child and they will always be your parent. They may need your help with the most intimate personal care. But you will never become their parent.

I saw this all the time when I was researching my book Caring for Our Parents. I had the opportunity to spend as long as two years with people who needed assistance and their family caregivers. I saw successes and sad failures. Often the difference was the ability of adult children to understand their role.

I was thinking about this after seeing Courtland Milloy’s column in this morning’s Washington Post  describing his experience as a long-distance caregiver visiting his parents in Louisiana.

He wrote, “Some elder-care experts say that when aging parents stop acting in their best interest, the grown children must “reverse roles” and simply make them do the right thing.”

As he learned, this advice is so wrong on so many levels.

To start, what is the “right thing?” Who are you to decide what is right? As a matter of law and, I believe, ethics and morality, each of us gets to decide the “right thing” for our own life, as long as we are cognitively able and our choice does not harm others.

A wise man once said it like this: “When I was 22, I did some things my parents thought were remarkably stupid. But I was an adult and they were my choices. Now, my parents may be doing some things that I think are remarkably stupid. But they have the same right to make mistakes as I did.”

Put yourself in the position of an aging parent. As you become physically frail and cognitively limited, you lose control of your life. All those day-to-day decisions that healthy people take for granted—when to go to the movies, when to eat, when to walk across the room and even when to go to the bathroom—are increasingly shared with others. It can be embarrassing and demeaning.

And it is why a big part of frail old age is about maintaining independence and respect.

Now comes your child. He may be 50 years old, but he is still your child. And he is saying, “Mom, you’ve got to go to the doctor. You’ve got to stop driving.  You’ve got to move to assisted living.” He may have just parachuted into town for a few days. He seems rushed and impatient. And you, who on some level still view your son as the 18-year-old who left home to go to college, are resentful, embarrassed, and maybe even angry.

Needless to say, this is not a great environment in which to make decisions.

What’s the alternative? As much as possible, share decision-making. As the adult child, never start any sentence with the words: “Mom, you’ve got to.…” Instead, try, “What do you think we should do….” Help them choose.  But work together as much as you can.

Of course, if a parent or other relative is emotionally or cognitively incapable of making decisions, you may have to step in. But that is much less common than many suppose.

To his credit, Milloy finally got it, despite starting out with that awful “reverse roles” advice.

Like the proverbial bad penny, this parenting your parents business keeps coming back. Years ago, when I was writing for Business Week, an editor suggested a consumer caregiving column. It would be called, you guessed it…Parenting Your Parents. I told her I’d love to write the column but the name had to go. That was the last I heard about the idea.

And let’s hope this is the last any of us hear about the worst advice a family caregiver can get.