One should plan realistic weight management and achievable goals.  You can begin with identifying high-risk situations that may lead to self-sabotage.  For example, don't fool yourself with the “one time won't hurt me” attitude, which can cause you to slide off track.  

Here's how you can prevent self-sabotage in these situations.  First, focus on the personal benefits of weight maintenance and the negative effects of giving in (like weight gain and self-blame).   Next, you should prepare early, before the special event or holiday.  Make your goals small, behavioral, and controllable.  For example, “I will choose the lower fat items and only make one trip to the buffet table.”  Self Monitoring your eating behaviors and weight will keep you aware of the results of your actions. 

A little preparation now can provide the ammunition you need to truly enjoy any special occasion.