I think a lot of it is mental. If you can train your brain to not want something anymore, you're set for life. Otherwise, you'll always be struggling and trying to find ways to trick yourself.
Personally, I found that as soon as I started learning about the true cost of most consumer goods (beyond money - environment, human health, child labor, sweatshops, etc), I stopped wanting my money to go to those companies. The Story of Plastic is one documentary I quite liked, if you're looking for somewhere to start. These days for the most part when I go to a store and see all the stuff for sale, I think of massive landfills, islands made of garbage, and all the videos I've seen of animals suffering as a result of our garbage (like the turtle with the straw up its nose, etc). There are a lot of zero waste bloggers/influencers who post tons of useful data and information about how to reduce your waste, alternatives to buying a new gadget, and so on.
Make it about more than money.