No matter how strong your willpower muscle becomes, it’s important to always respect the fact that it is limited, and if you overtax it, you will temporarily run out of steam. Don’t try to take on two challenging goals at once, if you can help it (like quitting smoking and dieting at the same time). And make achieving your goal easier by keeping yourself out of harm’s way. Many people are overly confident in their ability to resist temptation, and as a result they put themselves in situations where temptations abound. Successful people know not to make reaching a goal harder than it already is.

Resisting temptation is a key part of successfully reaching just about any goal. What we want to do is often the very opposite of what we need to do in order to achieve our professional or personal ambitions. This may sound a bit counterintuitive, but the very first thing you are going to want to do if you are serious about resisting temptation—even before you start working on building your willpower muscle—is make peace with the fact that your willpower is limited. It will always be limited, even if you get more of it through regular exercise. (Remember that no matter how big a muscle is, it can still be overworked.)

The problem is that most of us think we have more willpower than we actually do. As a result, we put ourselves in harm’s way, exposing ourselves to temptations that we assume we’ll be able to handle. For example, in one study of smoking cessation, participants who hadn’t smoked in three weeks (and were therefore well out of the physical withdrawal phase) were asked how confident they felt about resisting the desire to smoke in the future. They were also asked about whether or not they planned to avoid temptation—the situations (like being out with friends who smoke) that might increase their urge to smoke. The results showed that the more confident the former smokers were about their ability to resist temptation, the more likely they were to tempt fate. Several months later, smokers who did avoid temptation were less likely to have relapsed, while those who overestimated their willpower returned to their old habits.

Even if you have built up large reserves of willpower, you will not have much left for sticking to your resolutions at the end of a long day of putting out fires at work. (This is basically why Happy Hour exists.) Don’t kid yourself; during particularly stressful times, you will have a hard time staying on track. That’s why it’s so important to give some thought to when you are most likely to feel drained and vulnerable, and make an if-then plan to keep yourself out of harm’s way. Be prepared with an alternate activity, a distraction, or a low-calorie snack, whichever applies.

Also, do yourself a favor, and don’t try to pursue two goals at once that each requires a lot of self-control, if you can help it. This is really just asking for trouble. For example, studies show that people who try to quit smoking while dieting, in order to avoid the temporary weight gain that often accompanies smoking cessation, are more likely to fail at both enterprises than people who tackle them one at a time.

Finally, remember that it is far easier to abstain from doing something all together than it is to give in just a little and then stop. And you need more and more self-control to stop a behavior the longer it goes on. If you don’t want to end up having sex, it’s best to stop at the goodnight kiss. If you’re trying to lose weight, it’s best to pass up the potato chip bowl altogether. Remember the slogan, “Betcha can’t eat just one.” Lay’s wasn’t kidding.

Putting It into Practice: Stop Before You Start

1. If you have a bad habit you’re trying to kick or an impulse you are trying to resist, give some thought to the times and situations in which you are most vulnerable to temptation and how you can avoid them if possible.
2. Tackle major willpower challenges one at a time. (If people stuck to just one New Year’s resolution per year, they would be a lot more successful.)
3. Avoid thinking you can have “just one” or “a little bit” of something you really enjoy but shouldn’t have. It is easier to skip it entirely. Less fun, but much easier.