While it may seem clear that keeping a healthy diet has to do with eating less, for most people maintaining a healthy diet involves eating many more things than they normally consume. Portion control is certainly a part of a healthy diet, but it's more important to increase the intake of healthy foods and reduce the amount of empty carbohydrates, one of the worst things you can have in your diet.
While you can still eat many of your favorite craving foods on a healthy diet, you'll want to begin by shifting away from most of the foods you eat that don't provide any health benefit. Nearly everyone can get healthier by increasing their intake of fresh fruits and vegetables, and shifting away from white grain products toward whole grains like quinoa. While you can still enjoy a big slab of red meat every once in a while, you'll be on the right track if you mainly eat lean meats like chicken, and fish that's low in saturated fat. You'll also want to get some of your protein from non-meats like eggs and nuts.
One of the easiest ways to break a healthy diet is skipping meals, which can quickly lead to overeating and sometimes binge eating. Start the day with a substantial breakfast and try as hard as you can not to skip lunch or dinner; when you do, you're more likely to eat unhealthy and very large meals at odd times. Remember that a standard portion size for meat is only three ounces, so supplement your meat with a big side of vegetables and whole grains.
Eating cold turkey is fine, but using it as a way to change your diet rarely works. Consider making slow and gradual changes to your diet, such as trying to replace one diet pitfall or using a healthier ingredient each day. Over time, you're much more likely to find success in changing your diet in the long term doing this rather than just cutting out all the bad things you eat immediately.