If you eat something unplanned, if you eat too much, if you eat something decadent--tell yourself. From this moment on I am back on my program. The next thing I put in my mouth will be healthy and planned. I'm back on my plan with my next snack or meal.
Don't let one slip up derail you.You're building habits to last a lifetime. Don't throw in the towel today and figure the whole day is shot. The day is not shot! Start again now, don't wait for tomorrow or Monday to get back on your program.