I like the quote 'A journey of a thousand miles starts with a single step'.

The journey to any destination always needs a start and an end point, the direction of the journey can change, minute-by-minute, metre-by-metre or meal-by-meal.

We often focus too much on the end, in weight loss that might be a set number on the scales, and forget to enjoy the journey or learn lessons from the detours on the way.

It's practically impossible to drive across Coventry without a diversion of some sort, dieting is the same.  Some days will be great others not so great.  It doesn't matter as long as you take small and consistent steps forwards.  

Small steps form good habits and the results are more likely to last for a lifetime rather than until the 'number' is reached or the diet 'time' ends.

Don't beat yourself up if you slip from your diet but don't use it as an excuse to throw the towel in either.

Keep moving forwards.