The best apology for any action is to cease that action. If you say you are sorry for throwing your wife down the stairs, and then you do it again the next night, clearly you are not sorry. If you say you are sorry for drinking a roommate's beer and then you continue to finish off the 6-pack, clearly you are not sorry.
To avoid being a liar, do not ever say you are sorry unless you have a clear course of action to take to stop whatever it is you are sorry for. Otherwise, you are saying you are sorry without truly meaning it. But again, if you are hurting people without stopping, being a liar is the least of your problems.