That has been the hardest part for me! I think the biggest thing is to just keep trying. It's an ongoing PRACTICE, I still learn things almost 2 years into it.
Get back on plan when you hit a speed bump! Just because you have a bad day, or weekend, doesn't mean you can't turn things around. Even if your mistakes mean you don't lose weight that week, at least you are in control again.
Staying ahead of hunger I think is a huge part of it. Make sure you have plenty of foods on hand that you want to eat, but won't be tempted to overeat when the stress hits. For example, I have figured out that I do a lot better keeping lowfat or nonfat shredded cheese on hand than regular cheese (because I will stress eat it).
Always keep some healthy snacks with you. I bring a lunch bag to school/work with me every day that, in addition to lunch, has fruit/yogurt etc so I don't need to turn to the vending machines or fast food.
And, have a few staple low-points meals that you can count on to help balance out any higher-points meals that you end up eating on the fly.
Are you exercising? That really helps relieve stress. And it doesn't hurt counteracting the weekend indulgences either

I tend to exercise the most and eat/drink the most on the weekends. Unless I really go off the deep end they tend to balance each other out.