1. Credit Cards.
I'll keep saying it. Credit cards make people poor and stressed. Cut up your card now. Save for purchases instead of using credit. It's a big trap!
Don't go shopping without a plan. This goes for groceries, clothes, appliances - whatever you are going shopping for. Have a plan, write it down if necessary. Decide before you go how much you're prepared to spend and stick to it. Don't impulse buy!
3. Wait and reconsider.
You want to buy something. You really waaaaaant it! But do you need it? We are used to getting what we want, when we want it, right? If you decide you must have something, and particularly if it's expensive and not a necessity, I dare you to wait (a week, a month?) See how you go without it. After the waiting period, do you still really waaaaant it? It can be worth the wait, especially if you decide you don't actually need the item and can save the money instead.