It's an eloquent way to say "your works don't save you", but "Jesus did this". Further, if you continue to perform works in a manner consistent with believing you must perform these works for salvation, you are inherently stating Jesus' sacrifice was not enough.
Where "transgression against the law" is "sin", while you're still bound to the law for obedience, you are no longer bound to the law for the purpose of your salvation. If you break the law, if you sin, you are not lost, because of Jesus' mercy. But rather, if you adhere to the law, or endeavor to "practice to not sin", you're in danger of being lost, because you may be saying "Jesus' sacrifice was not enough" and further that "your works contribute to your salvation". It depends on the motives behind your actions.
While you still "sin" or transgress, and will continue to "sin", you are, at the same time, saved by Grace. Ephesians 2:1-10.