It's a great talk. I recommend having a nose through the Google talks series if you have a few minutes, there's lots of super-interesting stuff on all sorts of subjects, lots of which can be useful in addiction recovery - mindfulness, meditation and self-help of all sorts.
This talk is nearly an hour long and I recommend you give it a look if you have time - it's entertaining and backed by real science.
Here are the five points Ms McGonigal sums up with:
1 - Train your willpower physiology. So exercise, meditate, eat in a way that will give you sustained energy. This will help build your mental strength.
2 - Forgive yourself. This is a cliche of recovery, but apparently science backs it up. Don't beat yourself up if you fail and you're more likely to be succeed.
3 - Think about your future self in a way that feels real. Look at what you're going to be in the future and have a real sense of what you'd like to become.
4 - Plan for failure. This isn't saying prepare to relapse, but it's asking you to think about what might stop you from going to the gym or might contribute to you drinking or eating chocolate or whatever your positive or negative goal is. Have a plan for how you're going to cope with these barriers.
5 - Surfing the urge. Urge surfing is a mindfulness technique. There is a good explanation here.
I haven't read the book myself, but you may want to take a look. Here it is on Amazon: The Willpower Instinct: How Self-Control Works, Why It Matters, and What You Can Do to Get More of It .