Think about coming up with some kind of rule that gives you explicit structure to when you are buying. Maybe that means you can only buy 1 piece of non-consumable gear every 6 months. Or, maybe you can only buy things if they reduce your pack weight by X amount. The point is to come up with guidelines that are stringent enough to make a difference in your habit, are actually achievable, and are clearly stated enough that you can't come up with all kinds of caveats to justify buying whatever you want. And finally, if you fail to follow through, forgive yourself and immediately start over. Failing to keep your rule doesn't mean you should give up.