The keys to good nutrition are variety, balance, and moderation. Eating the same foods over and over can limit your access to the more than 50 nutrients required for good health. Even a healthy meal, such as cereal with skim milk and fresh fruit, is not nutritionally balanced enough to eat all the time. People in "food ruts" limit their chances for good nutrition.
There are no "good foods" and "bad foods". You can eat practically anything as long as you balance out your choices over time. Some foods like oil, butter, and fried foods are high in fat. You can still eat them if you balance them with low fat choices such as vegetables, fruits, and grains. Try to eat all foods in moderation. Too much of anything isn't a good idea.