We go through life assuming we're in charge of our own minds — until temptation (诱惑) strikes. Few things better illustrate how little control we really have. You can know exactly what you should do (decline the second slice of cake or the third cocktail), but that hardly seems to matter when the urge arises. More self-discipline is rarely the answer, though. Instead, if you can understand what's going on inside your head when temptation comes, you'll be far better placed to make a healthier choice.
Sometimes, you need to push yourself, the idea behind which, in psychology, is to make the better choice the easier choice. (School pupils eat more healthily, it's been shown, when the salads are within easier reach than the chips.) So, instead of relying on willpower, stop keeping ice creams in your freezer! Use StayFocused or similar apps to block distracting websites. Change your environment, and temptation will be a non-issue.
For every person, behind every bad habit, there's a reasonable desire: some people eat or drink too much because they're lonely, or smoke to get a break from a busy schedule. Once you've uncovered this underlying need, find a different way to meet it: call a friend; take a coffee break instead of a cigarette break. There's nothing wrong with the need — only with the way you're currently meeting it.
It's a strange truth that we'll break all sorts of promises to ourselves — yet most of us would never fail to show up at a prearranged meeting with a friend. Involve others in your temptation-resistance efforts, whether it's asking someone to check in weekly to see if you're sticking to your plan, or never going shopping alone if you're subject to impulse purchases. Best of all, launch a joint plan, in which two of you decide to give up a bad habit. That turns a challenge into a fun game.