His song "Deep Dreams" is a big hit circa 1926. Big enough for him to quit boxing, date Stella Graham, buy a lotta expensive stuff and then run outta money. He thinks he can just write another hit song, but his follow up, "Sweet and Hot," can't get any traction with the music publishers, and he has to go back to boxing. Stella goes back to dating Charlie Ellsworth and sends Johnny a "Dear John" letter on the eve of his lightweight championship bout. Distraught, he loses and gets injured badly. Stella marries Charlie, but he turns out to be a wife-beating drunk.
She leaves Charlie after two years, then sees in the paper that Johnny's in the hospital on his deathbed. Rushing to his side, he dies in her arms. His final song becomes a big, posthumous hit, "Why Did I Waste My Time In Loving You." Ouch!