I also think, as well as having a rock solid will power you should always incentivise your goals. For example, I put on 4 stones at college and carried it around for 10yrs. It was only when I saw 30 coming that I decided it was now or never. I decided on the size I wanted to hit and spent a decent amount of cash buying nice clothes of that size and my prize was that in the next six months I was going to fit in that. For me it worked. Actually once I conquered that problem I had enough self discipline to aim even higher and regain control of other areas of my life and aim for other unrelated goals. Everything you want in life can be achieved by self discipline, all you need is to start off with your first goal. Remember it's never too late and you can achieve anything you want with the right attitude, commitment and dedication.
Edit: it seems the most popular goal is to lose weight. I think it would be awesome if someone started a GH weight loss challenge so those who are interest could catalogue their progress over the months and motivate each other.