Uncle John said, "I got a feelin’ I’m bringin’ bad luck to my own folks. I got a feelin’ I oughta go away an’ let ’em be. I ain’t comf’table bein’ like this."
"I know this – a man got to do what he got to do. I can’t tell you. I can’t tell you. I don’t think they’s luck or bad luck. On’y one thing in this worl’ I’m sure of, an’ that’s I’m sure nobody got a right to mess with a fella’s life. He got to do it all hisself. Help him, maybe, but not tell him what to do."

– John Steinbeck

The Grapes of Wrath, Chapter 18. Uncle John believes that he has brought back luck on the family because of his sin in failing to get a doctor for his wife. Casy says that a man has to make his own decisions and he doesn’t believe in good or bad luck.