When changing the body to reach your goals you must understand that it is consistency in the long-run that will get you there. Don’t let one bad meal or missed workout derail your efforts. Your job is to keep those bad days to a minimum and then over time everything will work out. One bad meal or a missed cardio session will not make you fat and on the flip side one good meal or workout will not just make you lose weight.
Vacations happen, lunch outtings and birthday cakes happen, late nights at work happen, crappy workouts happen, colds and injuries happen.
Forget about it. Just do your best and never quit. In the end, as long as there are more good days than bad days, you will reach your goal.