In O. Henry's short story "A Retrieved Reformation," why did Jimmy Valentine stop burglaries?

Jimmy Valentine decided to give up his life of crime because he falls in love with a beautiful, small-town girl named Annabel Adams. He knows such a perfect girl will not return his love if she knows how he makes his living. 
As the story opens, Jimmy is serving time in prison for one of his latest safecracking jobs. 

He had been sent to prison to stay for four years. He had been there for ten months. But he had expected to stay only three months. Jimmy Valentine had many friends outside the prison. A man with so many friends does not expect to stay in prison long.

Jimmy hardly listens to the warden when he receives the pardon the governor signed reluctantly.

“Valentine,” said the chief prison officer, “you’ll go out tomorrow morning. This is your chance. Make a man of yourself. You’re not a bad fellow at heart. Stop breaking safes open, and live a better life.”

Jimmy's friends find it increasingly difficult to help him, as he learns from one friend.
Jimmy begins to sense his career of crime isn't as easy or lucrative as he thought it would be. Ben Price, the bank detective, is always on his trail. He is building a prison record. He is getting older. He is becoming notorious as the best safecracker in the business. It looks as though it will become easier and easier for Jimmy to be sent to prison and harder and harder for him to get out. He is in danger of becoming an incorrigible recidivist and growing old behind bars.
Jimmy decides to move out of his usual area of operations in Indiana and setting up a "front" as owner and operator of a shoe business in far-away Elmore, Arkansas. That is where he falls in love.

A young lady walked across the street, passed him at the corner, and entered a door. Over the door was the sign, “The Elmore Bank.” Jimmy Valentine looked into her eyes, forgetting at once what he was. He became another man.

Annabel is an inspiration. She falls in love with Jimmy, too, and he wants to be worthy of her love. Annabel symbolizes everything that has been missing in Jimmy's criminal life. She is the catalyst for his reformation. She is meant to symbolize everything a man can obtain by living a moral life and what he is missing by committing crimes.