Whenever I decide to try and cheat, like I'll go and buy a big bag of Twizzlers, or whatever kind of candy or cookie. I really hold it to myself debating if I should eat it or not. You just really have to keep battling it out. Ask yourself if you really need it. Hold on to the remorseful feeling you feel, and next time remember how you felt afterwards. If you find yourself with a snack you know you shouldn't eat, do just that. "I remember how I felt after the chocolates." And you will feel regret again.
So when I buy those things, the thing I try to do is battle it out with myself, and eventually I just give the snack to my cousins. Later on I crave it and want it back so bad haha, but it's not there, and I am free of regret. But still don't feel so bad, not all the time I do pass it up to my cousins, I eat it and feel that regret. We just have to learn from that bad feeling we have.