Life is not perfect - and your fat loss program shouldn't be either.  You can't expect yourself to follow your program to the letter every second of every day until you reach your goal.  If you do, you are setting yourself up for failure.  That is why you need to apply the 90/10 rule to your nutrition and exercise.

The 90/10 rule is very simple - if you are on your program 90% of the time, then you will not be hurt by the 10% of the time you are not on your program.  Your fat loss plan should have a minimum of 5 meals per day, with 6 meals a very good goal.  So following the 90/10 rule with 6 meals a day (or 42 meals a week) means that you have 4 meals a week where you can go off your program without halting progress.

So is that permission to eat 50 chicken wings and a 12 pack of beer for breakfast tomorrow?  Not exactly!  But if you wanted to have a couple of slices of pizza with two beers, or a burger, fries and a shake (NOT super sized!) then go ahead.  Maybe a piece of chocolate cake after your on-program dinner?  Sure!  Just get back on your program with your next meal.  I try to stick to 2 meals a week where I go off-program, but that can vary depending on my schedule.

Same rules apply to exercise.  Let's say your schedule permits you to work out 4 days per week.  So in a month, you have 16 workouts - and following the 90/10 rule, you can miss 1 or 2 workouts without derailing yourself.  However, I don't encourage you to skip workouts just because you can.  Save your "skips" for times when you really need to skip - like a poor night's sleep, illness, or hectic travel schedule.