“To live is Christ” puts us in a position to let the law do its work; the work of driving us to the cross. Now we can learn to rely on the indwelling life of Christ and the fulfilled law in us. And who knows, we might even have a a few moments where, by grace through faith, we actually do what we love – delight in God and love others.
When we know that we have all we need in Jesus. That every desire of the heart is satisfied by the omnipresent and omnipotent God (read the rest of Psalm 139). When we are freed by the love of God for us so that we can fearlessly ask to be exposed by God. Now we are ready to live. Now “to live is Christ.”
“To live is Christ” means that by our co-crucifixion with Jesus every individual sin has been dealt with forever. And by our co-resurrection with Jesus God’s indwelling infinite love and forgiveness remove the indwelling sin in our hearts as we deal with God according to his grace that has already dealt with all our sins.