How to reinforce my self-discipline?

[PretentiousHuman]

One of my New Year's resolution is to avoid dairy products and coffee because i have lactose intolerance due to my Crohn's Disease. But sometimes i crave coffee and desserts that has milk on it and i give in and consume it. Resulting to abdominal cramps and diarrhea. And if my family or co-workers are consuming those foods, i tend to be breaking my discipline and indulge to the foods that is hurting me. And guilt would creep in because i was never disciplined enough to stop my self from eating things not healthy for me.