The Gospel is not a message of doom and gloom. It is a message of joy and opportunity. The Gospel teaches us how to be forgiven of our sins and how to reach heaven.
However the Gospel is not permissive of sin. The Gospel does not tell us to remain in sin or to ignore sin. Instead it teaches us that God knows about our sins and that He wants us to be forgiven of them. The Gospel teaches us to put an end to our sins and to live by the Lord’s commandments.