Sometimes you feel like you can't push yourself anymore. Your willpower is depleted for the day and even if you use one of the tips on recharging your willpower battery described in this WIP article, it still may not be enough. You feel like giving up, just for this once - or maybe you consider dropping a specific principle altogether, even if you've only a couple days ago decided to honor it until a predetermined date.
Now, this time I'm not going to say I have a trick that makes you magically strong again. I have a whole new perstective on the matter. One that makes giving up seem, if not totally, then a little more acceptable.
Earn it. Earn the giving up.
What I mean by this is that if you feel like, say, having candy, and you've made a promise to yourself not to have candy (either ever again or until December for example), but you have such a craving for it that you think you can't resist it anymore, do something you don't like doing, or something physically challenging, before you go and get that candy. In other words, earn the candy. Earn the giving up. (The thought of the reward will give you just enough willpower to do it, even if you think your willpower is completely exhausted for the day.)
This will not only signal your subconscious that it has to work for pleasure - that you can't just let go on a sudden whim - so it will get stronger for the future. It will also have another effect: doing something you don't like to do, especially something physically challenging like running five miles or doing push-ups, might make you change your mind by suggesting to your mind that you're more than just a sugar addict - you're a strong individual who can do push-ups whenever they want and who doesn't need sugar to do it.
What's even more, if you decide you still want to give up after doing the straining task, you will feel like you've earned it. And an earned pleasure is infinitely better than an unearned pleasure. Your mind will know the difference and punish you with feelings of guilt if you haven't earned it.
Quite nifty, eh?