Sin comes with consequences. Yes, Jesus died on the cross to save us from our sins but the scars of sin still remain. Grace is an amazing gift (hence the song). Grace saves us from our sin but grace does not prevent us from sinning. That is up to us.
Lord, thank You for Grace that only You can provide but don't allow me to use Your Grace as a "Get out of Jail Free Card" that allows me to 'sin abundantly so grace may abound'.