Sorry to hear you've gained weight. One thing you can't forget is that watching what you eat once you hit your goal will never end. It will be a lifelong thing. You can't stop the diet.
In other words, when you hit goal, you can add more calories, but not much. You have to eat less than you did for the rest of your life or you will go back to the old habits you had that made you fat in the first place.
I know, it sucks.