Tutaminis is a very useful ability because it allows a Jedi to stop blaster bolts and lightsaber attacks. But how can someone learn this without losing a hand? This is how it plays out in my mind:
"Ok, so now I'm going to stab your hand with my lightsaber. Be sure to remember your training."
"Yes, master, I'm ready."
hand gets stabbed
Then the padawan screams because he did it wrong and got his hand chopped off by a lightsaber.