There are many, many, many definitions of sin out there.
But the definition I like best comes from a layperson at St. James' in Potomac, MD. "Sin is anything that removes us from God." I like the ambiguity this allows that the sign above does not. For some, drinking alcohol is sin because they are alcoholics and their control rests not in the God of all Creation, but in the 40 of Mad Dog on the passenger seat. For others, a glass of wine over dinner is a good compliment to their Filet, not an idol that replaces God.
As I reflect on the Collect for this Sunday and generally on the task of the prophet I'm realizing that their job has always been calling people to return to God and the only way to do that is to "forsake [abandon, renounce] our sins." As long as we hold onto those things that we place between us and God that restoration of relationship is impossible. Even though Jesus saved us 2000 years ago we still have a role to play in our salvation, we have to choose to accept it by re-turning to God by turning away from all those things that keep us from him.
This week has been one of a lot of pondering for me on the positive spin we can give the prophetic call, and I think using this definition of sin and forsaking thereof feels much more upbeat than the fire and brimstone escape from hell way of offering a prophetic word.