Step 5: Identify barriers
"There are going to be crises, external influences, times you have to eat Grandma's cookies," Neuhauser says. You'll have days when you can't exercise and days when you'll be tempted by holiday meals, and because you're tracking your progress, you'll be able to detect which events actually cause weight gain.

"Overwhelming evidence from many areas, including substance-abuse research, shows that situations trigger relapses," Alemi says. "You need to find out which situations make you return to old habits." Once you're aware that working late makes you too tired to exercise, for example, you can test strategies for leaving work on time. If you blow your eating plan because you dine out with friends who always order too much, try hosting takeout at your house and make sure you order the food.