After a long day of being oh-so-good, you might find you have no willpower left to resist any other temptations. (Make no mistake: your body creates willpower in limited quantities.) So does that mean you’re destined to flop on the couch and faceplant into an angel food cake? More From Prevention: Improve Your Willpower—Instantly Not necessarily, finds a new study published in the Journal of Personality and Social Psychology. Yes, we fall back on bad habits when our self-control reserves are empty. But we also fall back on good habits.  In one of five related studies, researchers from the University of Southern California and the University of California, Los Angeles surveyed business students about their daily habits for 10 weeks. Because the study fell during exam week— a time infamous for destroying self-control—the results would show how we rely on healthy and unhealthy habits during tough, frenzied times. Here’s what they found: students with strong habits both unhealthy (like eating pastries for breakfast) and healthy (like reading the newspaper every day) increased the performance of these habits during exam week. Even though they had a lot more reading material to absorb, those who generally read the paper continued to do so out of habit during test time. The idea that people revert to healthy habits during times of stress, instead of just unhealthy ones, isn’t something you hear a lot. “We think of ourselves as falling back into bad behaviors when we’re not exerting control,” said Wendy Wood, PhD, provost professor of psychology and business at USC and one of the authors of the research. “This study suggests that actually we fall back on automatic behaviors.” Habit formation is key. The behaviors we practice automatically on a regular basis deserve much of the credit for what we do when times get tough. It’s a powerful thought: if you just transform that sometimes run into a daily, scheduled habit, you’ll do it even when your motivation is shot. “The behavioral interventions haven’t focused much on habit formation, but that’s really what we need to do, because that’s what people will fall back on when they’re not controlling their behavior,” Dr. Wood said. Other studies suggest that to turn a behavior into an automatic habit, you have to do it at least 25-30 times, Dr. Wood said. Easy behaviors are more habit-forming, so start small—and stay away from temptation. “Get yourself out of situations that are associated with bad habits,” she said. If you’re trying to stop eating junk food in the car, then start a carpool, take a route avoiding fast-food restaurants, or ride your bike, she suggested. Do this often enough, and you’ve got a brand-new healthy habit.  “When you’re in that context at that time of day, the behavior that you typically perform comes to mind,” she said. “You can decide not to do it, but it’s typically easier to just go ahead and follow whatever is in your mind.” More from Prevention: 7 “Healthy” Habits That Aren’t