You should have either a pair of jeans or a swimsuit that you would like to get into and a picture of yourself when you were your ideal weight. This will provide the motivation you need to keep on going. Keep your eyes on the prize!
In order to break a plateau, drink a 12 ounce glass of water prior to every meal and snack you eat. It will fill you up a lot more and you will tend to eat less than normal, plus you will be getting your daily intake each day much easier.
Keep a set of running/walking shoes in your car. That way wherever you are you can get in some extra exercise. Also keep a towel handy too in case you get sweaty!
Lots of people have a sweet tooth and need a little "something" after they eat. If you want dessert, have it just watch the portion size. Take only a little bit and savor it. Take small bites and enjoy every one. And don't feel guilty. You didn't blow your diet, you are just human!