If you fall off the wagon, don't dwell on it, just get back on track.
Meal plan. Drink loads of water. If you are hungry, drink a glass of water before eating. Eat a piece of fruit if you are hungry. Think about why you are eating, are you really hungry or bored or emotional? Start walking or join a gym. Don't buy any chocolate, biscuits etc. and don't keep them in the house. Cut out soft drinks, juices and cordials.