I'm a precision guy: I like hard numbers. But I've learned with dieting that everything is an approximation anyway and soft numbers are healthier.

For instance, when giving yourself a weight goal, give yourself a range. My weight goal is to stay under 150 pounds. Sometimes I'm several pounds under that, sometimes I creep up right to that. But I don't sweat it: your weight will vary a little no matter what you do and it's not healthy to stress over such details. By giving yourself a range you can still be "on target" and yet there's flexibility.

I do the same with my calorie targets. Lunch, for instance, is around 500 calories. Sometimes it's only 475 if I'm not too hungry or happen to have a high-volume meal that's low-calorie, while other times I might be closer to 600. I find this a lot less stressful than trying to hit a specific number with each meal.