I'm not sure how relevant it is to Aikido, but once upon a time I was taking Ninjutsu and the sensei was both a practical man and a humorous one. We learned a lot of rolls and breakfalls in those classes because of the nature of the art, and one of our little challenges was to do diving forward rolls over a broom stick held four feet in the air. The floor was concrete though and many of us had reservations about diving head first at concrete. The sensei was appalled that his students were afraid. (An act he frequently put on for us.
) He had the oldest guy in class run down to the 7/11 and get him a 40 oz. beer, while the rest of us went about regular training. When he had his hand on the beer opened it, took one drink, and the proceeded to show us that he could do the diving roll over the broomstick: without spilling the beer. That was the most impressive fall I had ever seen. Here's the hitch: though the man could fall without ever worrying about injury, that wouldn't make his ukemi good for Aikido. He had no concept of CONNECTION.