Let's start with several hours to think about it ... shop ... pack things up ... review our schedules ...
What are you going to eat for breakfast? Do you take a nutritious snack for midmorning? What about lunch? And something healthy for the afternoon? Supper? What if you get the munchies later in the evening?
Are you going to get up early and go to the gym? Will you walk at lunch? How about a nice evening bike ride? Can you run up and down the steps twice for every load of laundry?
Think about it today. Plan for tomorrow. Imagine the sense of accomplishment you'll feel when you fall into bed tomorrow night, having made a healthy plan and stuck to it.