All successful diet plans allow for some error or a little bit of slack.  My rule of thumb is to expect 90% success each week.  For instance; since you will be eating 5 - 7 small meals a day, totaling about 40 meals each week, you can allow for 10% (or four) of those meals to be unbalanced, not on-time, or a cheat meal (something you normally wouldn't have for diet success).

90% success is so forgiving that it will work for anyone.  It lasts a lifetime and will leave the door open to learning opportunities, experimentation, and unusual circumstances; all typical obstacles of our busy lives.  

Success by 90% is outcome based, achievable, realistic, and forgiving; now who can't live with that?  Prepare your food, pack your meals, and be responsible for yourself - for in the long run - your consistency is what will shed those pounds.