Mark 1:15 (NIV)
Repent and believe the good news.
There's a popular misconception that since God has saved us, and Christ died for us, so everything is OK. It is, provided we take some action. Although we can't save ourselves, we still have to act on God's grace by repenting and believing. Indeed, our sins are automatically forgiven, but we still have to repent of our sins and believe that God has forgiven us. The grace to repent and believe is also from the Lord, but we have to act on the grace.