Motivation is kind of a tough nut to crack when you just don't have it, isn't it? Just make sure that your enthusiasm doesn't burn you out too soon. Remember that this new way of treating yourself is from now until the end. If you need to take a week off, take a week off. Take a few days to think about what you want to do for yourself and the reasons. Make a list of those reasons/goals. But everyday when you get up and before you go to bed, review the list. It may change as time goes on, it may not. Too many times, we make it easy to break promises that we make to ourselves. Why do we do that? Especially when we work so hard to keep promises that we make to other people. I don't know the answer to that. But, once I realised that fact, it's been easier to motivate myself without trying too hard... Just like we need a vacation from work, sometimes we need vacations from eating well, exercising, etc. Maybe it's a couple of days a month, one day a week - whatever. I know when I started, I took one free day a week. After a few weeks, I realised that I felt worse coming back from a free day than I did jonesing about it all week. Now I don't take as much liberty with my free days, but I still factor them in - one day every week. No guilt, no quitting.
I don't know if that helps you at all, but I hope you find something in yourself to help you. Maybe it's the smile your wife gives you when you update her with another pound or two lost. Maybe it's the way you feel when you realise that you just ran up a flight of steps AFTER coming back from a good long run. Whatever it is, find it and hold on to it.
-Frank