My husband and I made an agreement MANY years back that we don't buy anything until 24 hours has passed. It doesn't matter how much it costs .. it's whether it's a real need. We portray our lifestyles before our children and friends and if we can stop considering stuff as so important in our lives, maybe some of our other grand qualities will stand out and teach some character to our children about wanting to have so much.
One way we stopped this cold was to begin making a list of what we needed and only going to the store every two weeks. Some things we really needed then to work on a project, but by keeping our “lifestyle” it gave us time to dig around the house and become creative with what we already had to use. It's been a great way to expand the brain and if you have children at home, it's a great way for them to become thinkers and inventive themselves.
If you see something in a store, write it down to add to your list. I'll betcha when you get home 75% of things don't even get added. Another 15% get crossed off when you consider whether or not it's a need.
It's all about discipline and delayed gratification which we all need more of. The instant mentality has also ushered in the disposable mentality which is ruining our earth in many ways for the upcoming generations.