Some stuff for you to try:
- Pace yourself, by letting cravings go in manageable steps (If everyone else deserves compassion, so do you in your practice of letting go)
- Don't quit cold turkey, instead replace your habits with alternative activitites (essentially anything related to the eightfold path, not least meditation)
- Do Asubha bhavana (foulness meditation)
- Study dhamma (disperses ignorance on this topic, and is also conducive to comprehension/panna and hope/saddha, as alternatives to viriya/willpower)
- Ask your sangha (You already did)