You found dirty undies under the bed
What's going on: Three-year-olds may get a charge out of being difficult, but at heart they want to please you. They're old enough -- and this potty-training thing tends to be all-consuming enough -- to know perfectly well what it is you want from them. So if your child uses the potty with great success and then has an accident later, she may be too upset to tell you. Hence, the hiding of the smelly panties.
Let your kid know you're on to her. Don't just clean up the mess, thinking that'll save your child from shame. "Then she believes her secret is intact," says Peter Stavinoha, Ph.D., coauthor of Stress-Free Potty Training. Tell her you found her underpants, and add: "It's okay to have an accident! Just let me or Dad know if you do." She'll see she doesn't have to worry about how you'll react.
Take a breather. The tension may just be too much. Yes, it's tough (for you) to take a time-out, but putting your child back in diapers -- even for as long as two months -- will help her relax and make training easier when you go back to it.
Try not to care so much. Ha, right? Well, think of it this way: Potty training is a process. The end goal is great, but getting there takes time. Remember, this isn't about you. It's even harder for your child, so try to get rid of any nagging feelings that you're failing here. No one is. She'll get there.