Here's my trick:

Here's what I do when I am tempted to buy something besides groceries: I envision it on a garage sale table, slightly used. Would I still want it if it weren't shiny new and displayed to full advantage? Once you can see that item in your mind's eye as it might look in a jumble of junk in a second-hand store, the magic marketing around it fades away and it's almost always easy to walk away from it.

https://medium.com/minds-without-borders/decluttering-b1df5e3acd75