More from Prevention: 5 Women Who Gave Up MeatThe good news is that it’s possible to change your diet in a way that won’t drive you (or those around you) completely bonkers. Here’s how to stay sane on a new diet:1. Eat breakfast every day. Begin the day with a breakfast that includes whole grains, protein, colorful fruits and vegetables, and you’ll reap the benefits of a better mood–not to mention clarity of thought, better performance at school or work, fewer food cravings, and an all-around easier time managing your weight, says Elizabeth Somer, registered dietician and author of Eat Your Way to Happiness.2. Chow down at regular intervals. Eat regularly to steady your blood sugar: It’ll keep you from becoming irrationally irritable when the waiter forgets to serve your dressing on the side (what part of ON THE SIDE was not clear?) or when a fellow driver cuts you off (that %!^@# !!!). 3. Follow the 75% rule. Make sure that at least 75% of each meal and snack you eat consists of real, unprocessed foods. A 2009 study of nearly 3500 adults published in The British Journal of Psychiatry found a link between high consumption of processed foods (desserts, fried food, processed meats—the works) and the likelihood of depression. But here’s a reason to put a smile on your face: a diet rich in whole foods provides you with the most nutritional bang for your caloric buck—you get all the nutrients and none of the useless filler, whereas with processed foods you’re only getting a fraction of the nutrients per calorie.4. Pee pale. Drink enough water so that your urine is pale yellow, and you’ll stave off dehydration. The first sign of dehydration is fatigue, a slippery slope toward unleashing your cranky alter ego. 5. Swallow this: A moderate dose multivitamin, plus extra calcium, magnesium, vitamin D, and—especially for non salmon-eaters—a DHA supplement of at least 220 mg will help fill in any gaps in your new diet and steady your mood, says Somer. Vitamin D, in particular, feeds receptors in your brain that need vitamin D to keep hunger and cravings in check, as well as to pump up levels of the mood-boosting chemical serotonin. (Will vitamin D prevent your cold? Science’s new answer.)More from Prevention: 5 Delicious Veggie Recipes