Anyone can maintain a diet. All you need is persistence and determination. At least in my opinion it's relatively easy. Being vegetarian, vegan, raw, omniverous, or anything for that matter, is fairly simple if you want to do it.
However just because you are maintain the "right" diet, that doesn't mean you are healthy. It is possible to screw up on any diet. For example, a vegetarian who is eating lots of desserts, snack-foods, breads, empty grains, and other junk is in much worse health than a native Japanese habitant that eats meat several times a week.
Since the raw vegan diet has become somewhat of a "new phenomenon" (although it is not), I feel like I should address the health issues here too. It's easy to trick yourself into thinking that as long as you are only eating raw food, you can eat however much, whenever you want. However you will really wreck havoc on your body doing this. Overindulging in sugary foods (like raw sweeteners or concentrated sugar fruits) and nuts is very common and a heavy burden on your digestive system.
The key to any successful diet is to eat in moderation and eat sensibly. You've probably head of the book, "Why French Women Don't Get Fat." The key to their success is that whatever they eat, they eat in moderation.
A few closing tips that shouldn't go ignored include not eating late at night, not eating too much, not drinking within a 1/2 hour before or after eating, and balancing your required nutrients.
