I think one huge key to success is having a positive attitude towards how you eat, how you move and how you think about yourself. I know it sounds hokey, but it really is key to being successful.
How often do you hear people moaning about having to diet or get to the gym or how horrible they look, or how they can't eat something? A lot. You hear it in 'real life', you read it on blogs a lot. It can be a pervasive sentiment, and negativity breeds negativity.
Part of it is accepting things that can't change (like calories in calories out) and realizing that what you perceive as a negative is really a positive.
Instead of griping about your exercise - how about looking at is as being privileged enough to be able to move your body and take care of it? Those of us that can move freely need to be very thankful for that, because there are plenty of people who cannot and wish they could.
Or eating fresh fruit and veggies - don't complain about not eating the cheeseburger - see it as nourishing your health and your well being.
Something the Beck book has you do each day is to list all the positive things you did that day. It could eating right, having a great attitude, planning your meals, getting in exercise - or even just being able to stop a binge and get back on track. There is always some silver lining to be found, and the more positivity you project out, the more will come back to you.