Don't plan to start next Monday, or the first of the year. JUST DO IT!!! I planned to start my fitness/wellness journey so many times and experienced setbacks. Plan your meals for the next day and stay on track.
Made some bad choices on last night's meal? Don't discourage but encourage yourself!...
Consistency is the key to success. MAKE yourself do your workouts, especially. Things fall in line when you stay consistent with your behavior.
I have learned to prepare for the next day before I go to bed. I pack my lunch and healthy snacks so I don't have to mess with it in the morning. I have noticed if I have a healthy lunch packed, I won't go out to a fast food restaurant for lunch.