Hi traveller,
What Dominus has mentioned may look tough but if you really want to make sure that you don't revert back then some rigorous efforts are required. 24/7 vigilance may not be required but try to stay in a company whenever you are free. Make a note of all triggers and avoid them consciously.
Stay strong, don't give into any temptations as such. Its just a moment where you go weak and all your efforts go in vain so you have to be strong all the time.
Trust me, its not all that tough
Peace