What if I can’t stick with it?

I’m in my first week protocol and feel great both physically and mentally. I have really worked on identifying my thoughts and I have one that is really recurrent. When I think about future events, (upcoming trip to DC, upcoming tennis tournament that includes ALL the food and drink) I get very anxious. I keep thinking, what if I don’t stick with it? What if I fall off? I don’t want this to fail, too! Any advice on how to wrap my head around success during very tempting times?