This is the story of a boy (let's call him Johny) who lost his entire left arm in a car accident but didn't give up on his life.
He started judo training under the supervision of an experienced Sensei. He was doing very well. But he couldn't understand why Sensei only taught him one trick for the whole 3 months.
"Sensei," said the boy. "Shouldn't I be learning other tricks?"
“It's the only trick you know and the only one you'll ever need,” Sensei replied.
Johny could not accept the answer. But he trusted his teacher, so he kept working stubbornly.