One way to be truly sorry is to be sorrowful to the point of repentance. We shouldn't just say we're sorry because we're supposed to or because it's the "right thing" to do. We should say we're sorry because we are repenting of wrongdoing and trying to change our ways.
We should not be sorry for our faith in God, but we should be sorry and repentant because our faith in God's will shows us the way we should follow. When we know God's will, we know His plan of salvation for us, and we can be repentant in an eternal life with no regrets.
Be sorry and repentant in God so that you can live in salvation without regrets!
Thank You for Your forgiveness of my sins. When I stray from Your way, please help me to be truly sorry and repentant without regrets. In Jesus' name I pray, amen.