Instead of willpower, we should want to cultivate endurance . And endurance comes much more easily when we enlist and create supportive structures around us to help us to remain motivated to continually work towards change. It's sort of like the idea of getting braces on your teeth. You start out with crooked teeth and a desire to straighten them. You can't just use strength to twist them into place - if you do you'll have a mouth full of cracked and broken teeth.
Teeth are stubborn buggers that 'want' to stay where they are.
If you move them quickly they break. It takes a long time to move them this way - but it works. The same principles that work to straighten your teeth can work to straighten your habits too. You won't be motivated to accept this necessary 'pain' until you are humble and realistic enough to accept that it is truly in your best interests to do so. When we accept the realistic strength of our habits we are then in a better position to help ourselves change them.