WHY WHY WHY

Why is it we sabotage ourselves despite the best intentions? This boggles my mind time after time. I know what to do to lose weight and I start but I stop, WHY!!!!!!! I have a medical issue that prevents me from consuming certain things (or at least on a regular basis) but then I go ahead and get sloppy with my slight amount of discipline on the subject, even though I know it could be very detrimental for me. I do not know why I abuse myself in such a manner. I wish I wish someone could slap me upside the head and give me a clue. Maybe then I would stop.