Start with simple changes you CAN stick with. If you're not used to eating 6-9 servings of fresh fruit and veggies each and every day, then set a goal to eat 2-3 servings each day for one week. If you're not used to drinking 8 glasses of water, then set a goal to drink 2-4 glasses each day for one week. If you're not used to regular exercise, then set a goal to walk for 30 minutes each day for one week. Once you've achieved those goals, then you create a new set of goals.
Don't look at weight loss or good health with an all or nothing mentality. Any healthy thing you do for yourself IS a step in the right direction. As the old saying goes,"don't throw the baby out with the dirty bathe water". If you have a nutritious breakfast and lunch, but think you blow it at dinner, give yourself credit for eating the healthy breakfast and lunch.
With time, your healthy habits will creep over into the dinner. The point is that you are trying to change habits learned over a life time. that's not going to happen overnight, a week, a month or even a year. Change takes time. thus the need to be patient with yourself and your body.
So, do you think you could eat 2-3 servings of fresh fruit and veggies each day for one week ? Do you think you could drink 2-4 glasses of water ? Do you think you could take a 30 minute walk ? If so, then you're on your way to a healthy lifestyle !