As far as maintaining weight, this is much more about habits than anything else; many of us (certainly those with weight issues) will tend toward overeating if allowed. Regular mealtimes, recipe planning, and even calorie counting can work to mitigate this tendency. Exercise, too, is often a very important part of this; many find it easier to maintain a target weight while keeping an exercise regimen. Part of it may simply be that those who are disciplined or otherwise able to get regular exercise may also have better eating habits. But I think there is another effect that makes it easier to maintain a calorie balance when you have regular exercise.
A big reason that people are attracted to unhealthy foods is because they taste good and are immediately satisfying. They are, in essence, a coping mechanism - something that makes us feel better (temporarily).
Exercise can be a healthier remedy to bad food to making you feel better. When you exercise and are feeling better, you are naturally more inclined to be attracted to healthier, more wholesome foods.
I expect that, for many people, it's not a simple matter to just eat better in and of itself, and stick to it. Stress and bad feelings need to find a coping mechanism, and they will find one, whether healthy or unhealthy - it really can't be avoided. You need to either reduce your stress, or find healthier coping.
I've lost maybe 3 lbs.
The goal of exercise or diet shouldn’t be to lose weight; it should be to increase fitness and to decrease body fat percentage.