My high school basketball coach used to award a free chicken sandwich coupon to the players who took a charge during a game. To those of you not familiar with a charge, it is when you sacrifice your body and let an opposing player run into you to draw a foul. It usually hurts so most people are reluctant to do it. I thought it was funny how much this simple reward could motivate some of us. We might not take a charge to win the game for our school, but we'd sure as heck do it to for a sandwich!
I've seen similar situations in life where people will go to great lengths and work hard for small rewards, but they are reluctant to do it for their own health or for the many obvious benefits that would come from doing so. I like to make charts to track my progress towards goals. Some people might think coloring in boxes is silly or juvenile, but I will milk it for all its worth since it helps me make progress. Rewards don't have to be big or expensive to motivate most people. Some times people will work harder for the small things since they are so attainable and believable.
It requires discipline to only reward yourself with some of these small things after you hit your goal. I've heard of successful business people who may have millions in the bank, but they refuse to buy the flat screen TV or mountain bike they want (which could easily afford) until they hit a specific goal. Some aspects of getting into shape are just as much a mental battle as their are physical and that is why rewards can be so helpful. Overcoming these psychological battles with your self can be difficult, but as you consistently exert yourself, your self esteem and confidence will increase.
Caution: If you are going to reward yourself for your efforts, make sure the reward it appropriate for the level of achievement. You obviously wouldn't go on a vacation to Hawaii for eating 5-7 servings of vegetables during the week, but you might go out to eat to as a reward for a week of healthy eating. If there is something you really enjoy doing, use it as a reward for good behavior. Some simple rewards include watching a favorite TV show after you exercise, or buying new clothes when you slim down a size. Just find some kind of carrot that motivates you and dangle in front of you as a reward for when you accomplish your goals.