I think this song is talking about how, as Christians, if we walk away from what God has called us to and what we should be doing as Christians, then people will just scoff at us.
People will realize that we tried to be changed, but in the end we failed and have ended up as empty people. But in the end, because of salvation, no matter how far we've fallen, because of God's forgiveness, we can still go to heaven.
In a way, this song is a challenge to people. It encourages them to keep on in their Christian life, and, no matter what mistakes they've made, they can still come back to God.