What you expect is what you get.
If you find your self-control is slipping here, there, and everywhere, what can you do to restore your good self-control? One not so surprising thing you can do is get in a better mood. A positive mood has a restorative effect on self-control. When in a positive mood, you expect to have more energy and to be more active. In a negative mood you expect to feel more depleted and run down.
So when trying to lose weight and your self-control is down a notch or two, sharpen up your expectations for replenishing your self-control energy by finding some way of getting into a genuinely positive mood.