Wow, impressive loss, blooming well done you!!!
I wonder if you have got to a point where you feel almost satisfied with loss so far, so you have lost your will power and motivation to be strict with yourself.
I also wonder if after 12 months of being strict with yourself you've felt like you deserve a break.
Positively at least you know you can maintain your weight loss, which should give you confidence boost!
I know it sounds pathetic and materialistic but perhaps a piece of jewellery, dress or a holiday could motivate you to carry on with the last stone.
Or writing down your goals and why you want them so much, sometimes seeing things in black and white makes them more real. x