What is your diet like? If it's too restrictive it's bound to cause cheating and binges. Your have to make sure it's a balanced diet. You can survive without sugar however you do have to have some protein and keep your blood sugar levels even in order to feel sane. Without knowing what your diet is its impossible to know if it's even appropriate to say "you can do it!" Because some diets can be ridiculous.
“If you try to lose weight by shaming, depriving and fearing yourself, you will end up shamed, deprived, and afraid.” Geneen Roth