Regression

How common is learning regression in young kids? It seems every time they move one step forward, they will take two steps backward. They'll master one thing, then seemingly forget and have to start over. In my kid's case, it is potty training and social acclimatizing (I thought I made that word up, but it made it through spell-checker). At one point in time, she was 90% potty trained. She wore underwear, she went on her own without prompting, and I was happy and relieved. Now, she'll fight when I tell her to use the potty. She's back in diapers, and the potty seems to be a strange new thing, akin to a discovery made by a Star Trek landing party. And she's wearing the Red Diaper.

Secondly, today, and yesterday, she hit another kid. She's gone weeks without getting up into someone else's grill. Now suddenly, the World is Not Enough. Is there such a thing as regression? Why does it feel like I am stuck in one of those Ground Hog day infinite loops where I gotta teach the same Sesame Street lessons every day? If I wanted to teach the same basic concepts, day after day, I would've become a high-school civics teacher.