Hi Lolly,
Welcome to Social Slimmers
I agree with Angel once done you can't change that day but you can change tomorrow ... just move onwards and upwards from it. I used to beat myself up, I've stopped.
Are you really strict with yourself? Sometimes if you are too strict these days are more likely to creep on us. I have learnt if I want carbs (for me I try and stay low carbs) I have it, if I want something sweet I have it. I try and have good choices of both in so it's not too bad but if I don't then I end up on one day where it ALL goes down hill!