Stop going into the store. That helps. In addition, allow yourself to buy a fat quarter, just not yardage.
I know and get it. I actually have a goal now as I'm buying a Bernina tomorrow, so that is the end of my fabric purchases until it's paid off next year. The only exception is fabric needed to finish a project. Even swaps are on hold because nearly always, I need to buy at least background fabric.
If you can't help yourself, then make a goal. Leave the checkbook and credit card at home. Take $30 and once a month, that is what you have to spend. When it's gone, you can't buy more.
If you tend to buy online, then you need to DELETE all your links to fabric places. They will still be there. There will still be cool fabric.
Finally, ask your enabler friends to help you by not reminding you of sales or reasons to go to the fabric store. If you go shopping, remind yourself - is this a want or a need? If a want, don't buy it.
It's really hard to discipline yourself when you are in a habit of buying whatever you want, guilt later.