1. Focus on what you will do instead of what you are trying to resist. Example. "I will take a brisk walk on my break." instead of "I will NOT smoke." Fill your day with positives. Instead of, "I will not be short tempered." try "I will live in the moment and practise patience." 

2. Plan. Temptations to deviate from your goal are everywhere. Anticipate and plan ahead how you will handle them. Example. "When Joyce brings baking to the office, I will walk away and reach for my apple in my desk drawer." Decide what you will eat, at what time of the day. 

3. Baby steps. You will be far more successful if you take baby steps. Want to read more? Don't start with a goal of 1 book/week. What can you reasonably achieve? 15 minutes a day? Start there and build up. Success breads success. 

Go for it!