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Don’t beat yourself up when you eat meat/cheese/eggs/fish, but do pay attention to what your triggers are.
For instance, I know that I’ll crave pizza if I drink beer. Now I make sure that, if I’m going to drink, I have a plan in place for dinner. This keeps me from falling back to my “default”.
Most of all, make sure you’re enjoying yourself. You don’t mention whether you cook or not, but I’d recommend The Veganomicon. The recipes are approachable, the ingredients aren’t too obscure, and the food is delicious.