Don't worry about eating a perfect diet, just try to eat "mostly good food". A lunch that includes a salad and an apple, isn't ruined by a bag of potato chips. It's still mostly good.
One of the best things you can do for your diet is eat a variety of foods. Many of us get in food ruts, particularly if our time or cooking skills are limited. I know men whose fruit and vegetable selections consist only of apples, bananas, lettuce, and potatoes.
These are the foods they grew up with, because they were cheap and available all year. We have a lot more options now. You're shortchanging yourself nutritionally and limiting your enjoyment of foods when you don't take advantage of the wide variety of foods available to you.
The other thing you should look for in your meals is an appropriate balance of nutrients. Dietary recommendations are to consume 55-60% carbohydrates, 30% fat, and 10-15% protein.
Every meal doesn't have to follow these proportions, but if all your meals center around a big hunk of meat, you're not eating a balanced diet. Most men eat less than half the recommended amount of fruits and vegetables, but far exceed protein and fat recommendations.
Portion control is another important issue, especially if you don't always make the best food choices. A huge portion of salad or broccoli isn't going to be an issue, but a huge portion of fried chicken or nachos is a problem. Basically, the less careful you are about what you eat, the more careful you need to be about how much you eat.
You also need to think about the trade-offs you are willing to make. You can eat whatever you want and as much as you want, but the trade-off is likely to be poor health and shorter life span. You can be very strict about what you eat, but the trade off is likely to be your enjoyment and satisfaction. Striking a happy balance should be your goal.
For specific meal planning tips, visit the following pages:
Better Breakfasts
Sensible Lunches
Easy Dinners
Snacks
Beverages
Menu Plans