In "A Retrieved Reformation," what does the conversation between Jimmy and the warden tell you about Jimmy?

Jimmy is young and cocky. He has a winning personality. Everybody likes him. The warden takes a special interest in him because he sees that Jimmy is a cut above the hardened cons he has to deal with every day. Jimmy seems to be ignoring the warden's well-meant advice, but some of it must be making an impression on him. No doubt Jimmy appreciates the fact that the warden likes him and is trying to save him from the downhill path of a life of crime. Jimmy is acting cheerful and confident, but he has been sobered by the fact that his stay in the prison lasted much longer than he expected. He is beginning to realize that his expertise as a safecracker is a handicap as well as an asset. It is becoming easier to get arrested and harder to get out. He may have important connections on the outside, but these people can forget about him very quickly if he becomes so notorious that he is no longer a good person to know. It is appropriate that the story opens inside a prison. It illustrates the fact that Jimmy is not as smart as he thinks he is. The best thing the warden tells him is the following:

“Now, Valentine,” said the warden, “you'll go out in the morning. Brace up, and make a man of yourself. You're not a bad fellow at heart. Stop cracking safes, and live straight.”

A man who has the intelligence, personality, and talent to be a successful criminal can use the same intelligence, personality, and talent to become even more successful as an honest citizen. When Jimmy decides that he is getting too notorious in the Indiana area and moves to Arkansas, his falling in love with Annabel Adams is not exactly a cause of his decision to reform but more of a catalyst. He has been changing gradually without even realizing it. He has been more or less unconsciously to the realization of the truth he expresses in a letter to his old friend.

Say, Billy, I've quit the old business—a year ago. I've got a nice store. I'm making an honest living, and I'm going to marry the finest girl on earth two weeks from now. It's the only life, Billy—the straight one. I wouldn't touch a dollar of another man's money now for a million. 

Jimmy is still in danger of having his past catch up with him. His nemesis Ben Price is on his trail because of the four bank jobs Jimmy pulled off in Indiana right after his interview with the warden. But Ben Price decides to give him a break after witnessing how he sacrifices his whole future in order to rescue a little girl who has accidentally become locked in Annabel's father's bank vault.