If you have quit before, good. That means you already know how it goes wrong, and we can plan around it.
Here is the pattern. You start strong. Week one is easy. Somewhere around week three something at work blows up, or you get sick, or you eat the wrong thing at a dinner and write off the week.
So the plan is not "be perfect for 30 days." The plan is "be back within a day, every time."
Week 1: just talk. Do not diet. Do not change anything. Tell Scully what you eat and how you move for a week. Say it in plain words. You are collecting a picture, not trying to be good.
Week 2: pick one thing. One. Protein at breakfast, or a 20-minute walk after dinner, or stopping the 11 PM snacking. Not four. One.
Week 3: expect the wobble. This is the week most people quit. Plan for it out loud. "If I miss two days, I will do X." Tell Scully when it happens. A missed day is a data point, not a verdict.