I totally agree with this statement. Once you've made that "lifestyle change" and start working out on a regular basis and eating healthier, it becomes more of a habit and is more natural. Don't get me wrong, I still think regardless of how long or well you've been able to adapt to these healthier lifestyle changes, it does still take some encouragement and motivation to keep going; however, I think once it becomes a habit it may be a little easier.
For me personally, because I've been doing this for two years, it is a lot easier for me. Yes, I have days or moments that I eat my pizza or I have a piece of cake; but, because my overall habits have changed, it's a lot easier for me to control when and how much I eat of these things. I mean pizza (or any Italian) is my all time favorite, and from time to time I do want to eat some. I have a piece of birthday cake or dessert at a special family dinner. But I no longer eat these things in large portions, nor do I eat like that on a daily basis.
So, once you've been motivated to get started and make the changes you need to make in order to become healthier, stay with it! Because once it's become a habit, it'll be a lot easier and worth it!