This secret is based on a quote I found a while back that says, "Don't trade for what you want most for what you want at the moment." I can't remember where I saw it or who it came from, but it has stuck with me. This can apply to food, exercise or anything that might hamper your long term goal for a short term satisfaction.
For example... while grocery shopping I have CRAVED junk... but I said to myself. "I do not want to trade my fit/healthy body that I will have someday, for that chocolate eclair that I want right now." When applied... it really does work.