I write it down. Whenever I feel very down and want to eat I start to write it down. Most of the time it's not even real hunger, it's more emotional hunger, like boredom. After doing that I drink some water and try to focus on something I really enjoy doing (playing a game on the pc, watching a film or some programmes, drawing) anything to keep me busy.
If that doesn't help I look at my little list of gifts I'll be getting from my OH when I reach certain goals. It keeps me motivated ^^