Paul wrote to the believers in Rome (12:1,2) that their transformation should come through having their minds changed. That is a picture of repentance – “metanoeo” – changed knowledge.
Every time you respond to opportunities to do things an old, unconverted-to-Jesus way, if you do it the new, “like Jesus” way, you have proven you have repented. We change our behavior slowly sometimes because we have so many different responses in different situations. If Mom is watching, we have one set of values. If a policeman is watching, we have one set of values. If a friend we like to do stupid things with is watching, we may do things differently. If no one is watching, we use another set of guidelines.
Until you have changed all those values, and always respond the same way, your behavior is lagging behind your mind with regard to change. Until you change all of your mind, you will not change all of your behavior.
When you are converted at the level of your values, your behavior will change to a new normal. At some point in your past, if I had offered you a choice between a $50 bill and your favorite flavor of ice cream, you would have chosen the sweet treat with no questions. Then one day you learned that the money was more valuable.
Set your mind on things that have value in heaven.