There is a real and definite progression when someone goes through the stages of change... what you are describing is totally NORMAL. And yes, it applies to recovering alcoholics, dieters, drug users, exercisers, etc. Anyone making lifestyle or health changes.
"Your head messing with you" is the major reason why people give up when they relapse, which by the way, is part of the cycle of change. It's also the reason why people don't listen to their doctor or comply with medication routines, even though they know there might be life threatening consequences.
You've achieved a great amount already. Be kind to yourself.