IMHO, practice moderation in all things, including moderation. Do I need to cut out ALL carbs? Should I really consume NO fruit? I can NEVER enjoy a good beer? Those rules would simply never be sustainable for me.
I generally stick to what I would call a healthy diet: mostly fruits and vegetables, eggs, whole wheat bread/pasta, small portions of meat (usually fish) with most dinners and some lunches. At the same time, I don't feel at all guilty about grabbing a couple beers or ordering the wings if I'm out to dinner or happy hour with friends. This system has been working for me because I also exercise regularly: alternating between jogging and hitting the gym most days of the week. Yes, it clearly took a bit of discipline to get into these habits. But now it's just become a lifestyle I find easy and enjoyable to maintain. What hacker doesn't appreciate a good challenge with such immediate and important results as your good health?