"Knowing I can choose makes me feel more positive and in control of my finances."
How : You must change your habits slowly. Ussually, students shopping for emotional reasons, not because they needed things. You must come up with a strong positive goal to motivate you to shop less. Thinking about the negative impact could make me feel depressed, which would make you want to shop.
Lessons & tips: You need a strong motivating goal. Shopping is fun after all, and the amount doesn't really matter as much as you thought it would. When you wanted something more expensive you must try to save up your weekly amounts until you have enough. Put the spending money in an envelope and write down your purchases to keep yourself honest.
Resources: Create a budget. Basically you figure out what you spend your money on in a typical year, then break it down to monthly amounts. It is much easier than you thought and you can see the impact of your spending. $10 a week easily adds up to $500 in a year. There are better ways to spend your money.