Unfortunately, no one has an unending supply of willpower. If you are struggling, then you will have to avoid the temptations you find irresistible. If you're serious about losing weight and keeping it off, you might need to cut ties with certain situations or overindulging frenemies, at least for a little while, maybe forever.
Changing your mindset to being a victor of your life, sets the stage for you to regain your power. In this state, you are more likely to also stay positive in the face of challenges, experiencing less fear as the stress response is more controlled. More importantly, you are more likely to access your inner fire of motivation -- that fire that drives you to win and achieve.