Therefore, if you have been raised with Christ, keep seeking the things that are above, where Christ is, seated at the right hand of God.
Colossians 3:1 (NASB)
When you come to Christ, although He asks you to come as you are, He does not expect you to retain the old sinful nature that you lived with. By His death on the cross, He purified you, sanctified you and saved you from the condemnation to come. It is your decision to accept His sacrifice and renounce your life of sin that will enable you to enjoy this wondrous grace.
However, this decision translates into drastic action on our part. Put off the old man who corrupts himself with deceptive lusts to put on the new man, as mentioned in Ephesians 4:22-24.
What does it mean to put off to put on? It is not a job you can do on your own, but the Holy Spirit will guide you through this process if you walk in obedience to His voice. So, to do this, you have to put aside everything that distances you from God and renew your mind through the study and meditation of the word. You will see the change happen on its own.
It is to this new life that Jesus calls us all.