1. Make Your Commitment More Tangible
Write down on a piece of paper that your spending is out of your control and list the ways that it's causing problems in your life. Now tell someone else. Pick someone that loves you, or that you view as compassionate. Sharing this actually eases the shame and helps to make the problem seem more manageable. It also reinforces your commitment to change your behavior.
2. Stop using excuses or blaming others.
Marketing is not mind control and other people really can't make you buy things. It's good to know your triggers and avoid them - but at the same time you must get clear on your own power and stop giving it to others by blaming them for your actions.
3. Get to the root of the problem.
Overspending isn't really about "stuff," it's about masking depression, anxiety or anger. You can find a local therapist that specializes in spending problems through the Psychology Today Therapist Finder. Enter your zip code and in the section where you're describing what you'd like help with select the "Impulse Control Disorders" option. Don't worry, it doesn't mean you have a disorder - that's just their sorting mechanism.
Psychology Today Finder: http://tinyurl.com/6qe96
4. Improve your life.
Take action to get more satisfaction from life - at the very least find a meaningful distraction while you're sorting through the problem. Spend more time with friends, get a pet, volunteer, try new hobbies, take a class or get more exercise. You've heard them all before. That's because they really do work. You might find that something was missing in your life and discover new ways to feel rewarded, loved and complete without shopping. At the very least you'll have less time to shop.
5. Stay mindful and aware of your commitment to yourself.
Use lists and planning tools to give yourself the structure you need to stay in control of spending. Notice each small difference in your spending and take pride in this achievement. When tempted, remind yourself of your successes.