Q. My 3 1 / 2-year-old daughter was successfully potty-trained when she went through a three-day diaper-free “boot camp” six months ago. There were very few accidents in the beginning and no accidents since then.

I say that there are no “accidents,” but my husband and I have had to deal with a lot of “on purposes.” Even though we know that our daughter can control her bladder easily, we’ve watched her deliberately empty it when she was unhappy with us for putting her in her room for a timeout.

Our latest challenge occurs at night. My child wears a diaper when she goes to bed since she pees during the night, but she now seems to move her diaper out of the way so she can pee directly onto her bed. It happened again last night. She seemed happy when I sent her to her room at bedtime, but she immediately emptied her bladder onto her clean sheets, even though she had just watched me change them.

I’m all about positive reinforcement, empowerment and having a drama-free home, but this behavior has been going on for weeks — maybe for months — and I don’t know what to do next. We encourage our little girl to go to the bathroom before she goes to bed, but I can’t force her to pee when she says she doesn’t need to go. That would be against my better judgment, and it wouldn’t work anyway. But what do we do?

A. There comes a time in every parent’s life when she suddenly realizes that a child who can walk and talk and recognize a few letters is not a baby anymore. And that’s when she says to herself, “That’s it! NO MORE DIAPERS!”

(Hadley Hooper/For The Washington Post)

Although the boot camp trained your daughter quickly and well, you could probably have trained her just as quickly if you had adopted a determined, no-nonsense attitude and promised to give her a Thomas the Tank table or a trip to the amusement park. Bribery nearly always works as long as the child is 18 months or so, isn’t constipated and isn’t bothered by milk or an allergy that makes her bladder malfunction.

A 3-year-old who is healthy and yet refuses to pee in the potty (or eat what you eat or sleep where she is supposed to sleep), however, probably has a control issue. And if she does, then her mom has one, too. Power struggles often show up when parents give too many unnecessary orders to their children, especially when they are between 15 and 30 months. A bad parent-child pattern, once set, can last for years, and so can the tantrums and the tiresome arguments that come with it.

Even if you have boxed yourself into this corner, don’t worry. You can get out of it quickly by giving your daughter more independence, teaching her to take care of herself, giving only one to two timeouts a week, and ignoring her small failures whenever you can. Once your child has no reason to rebel, she will pee in the pot just like you and her dad.

If you’ve never given your little girl many orders, however, look at the calendar. She may be having her “on purposes” because all children between 1 and 6 fall apart — and stay apart — for a few months every year, which usually happens about six months after their birthday. Even though your daughter’s behavior is driving you batty, this annual meltdown gives her the psychological space she needs to think and act with more maturity, the way a snake needs to shed its skin so its body can get bigger.

This rough patch will be smoother if you lower your standards, prevent problems before they start and laugh about your daughter’s “on purposes,” because it’s always better to laugh than to cry.

And for those parents who are tired of changing diapers, it’s time to train your child on your own and to follow Suzanne Riffel’s e-book, “The Potty Boot Camp” (Booklocker.com, $4.60), which is a short, intense program with many, many fans.

Whatever technique you use, keep it short and make harmony your goal.

Questions? Send them to advice@margueritekelly.com.

Also at washingtonpost.com Join Kelly on Thursday at noon for a live Q&A about parenting and other family relationships at washingtonpost.com/advice , where you can also read previous Family Almanac columns.