Like riding a bicycle, turning cartwheels is a permanent skill. Can always be perfected, can't be un-learned. Here's the learning process (below,  with my sister Mimi), in my Ashland, Virginia back yard, circa 1944. Some 50 years later, thinking it seemed an interesting thing to do, I called the Circus Center of San Francisco (then known as the San Francisco Circus School) to inquire about a course they were offering in Circus 101. "Can a fairly fit, reasonably flexible mid-sixties little old lady take your course?" They said, in effect, "If you've got the enrolment fee, we'll work this out."

The course was a blast. I found very quickly that I don't do upside-down very well without throwing up, so there went the standing-on-your-head. I mastered the rolo-bolo, managed to juggle a maximum of about two items for maybe a minute, and if I failed miserably at the fancy tricks I aced the balance beam; you grow up on the railroad tracks, you learn balance. And I always got to be the top of the pyramid, because nobody wanted to step on me. 

The upside-down problem wiped me out of a substantial portion of the course, but I still like having Circus 101 on my resume. And at graduation, I cartwheeled across the room