Back story: I used to walk on my toes, untill age 13. My achillestendons were too short, so I could not get my heels on the ground. From age 10 to 13 my PT tortured me so I could finally walk "normal" (I still have a spring in my step, I am told). Even though I am 40 now, I still notice it in my flexibility, some moves are still quite difficult.
Take child's pose. I love it, but my ass was always just hovering over my heels. With my forehead on the floor there used to be a gap between my thighs and heels of about a fist high (thumbs facing up). Today I did the latest stretching routine: https://www.fitnessblender.com/videos/static-stretching-workout-for-the-lower-body-and-lower-back and added a child's pose at the end. My thighs touched my heels!! Just ever so slightly, but there was contact while my forehead was on the ground!! It made me smile. It took a long time, but it finally happened. So happy!!