The song is largely autobiographical; Haggard's father died when he was nine years old, and his mother, a devout member of the Church of Christ, tried to keep him on the straight and narrow with a strict upbringing based on her conservative values. This didn't sit well with Haggard, who said he was an "incorrigible" child and constantly rebelling against her ("Despite all my Sunday learning, towards the bad I kept on turning").
He was always hopping on freight trains ("The first thing I remember knowing was a lonesome whistle blowing"), an early indicator of his itinerant outlaw personality. He got into trouble for offenses like shoplifting and writing bad checks. Stints in reform school didn't help, and in 1957 he landed in prison for burglary, where he spent his 21st birthday.
In this song, Haggard takes full responsibility for his choices and takes pity on his mother, who did the best she could ("No one could steer me right but Mama tried").