Ha - I wish I had an answer for this - once I've let slip, I find it really tough to get my groove back...I guess that I'd just think long and hard about why I wanted it so badly - I've achieved my blood-pressure goal and I'm down to a 14-16 - but this next bit is about me wanting to run long distances again and to be a healthy BMI by the time I hear whether I have a marathon place or not. So I'm thinking ahead in a 3-6 month chunk. Also - when I am getting back on it, I trick myself by saying 'Just do it for 5 days. A week. 10 days, may as well do it for a month. If I do it for 2 months, that's around 2.5-3 stone. It's only 2 months.
Also on this diet I am saving about 300 quid a month in not eating out and socialising and that extra money is coming in very handy!