Sick of dieting :3

You know when you just have one of those bad food days, and then it turns into a week and before you know it you've gained a stone and you want to die? Ha. Slightly dramatic, but this is how I feel. I've been dieting for about 5 years. I get thin (as above) and then I'm so happy with being thin I eat loads and it's back to square one, a vicious vicious circle. I wish I could just click my fingers and then be thin forever. Is there any magic solution? I've gymed it up before and I lost interest after I didn't see any results after a few weeks. Tomorrow is a new day, but as for tonight, I think a Domino's may just cheer me up ^^