I think I am a poor role model for curbing makeup acquisition! Probably true for most of us here. If I want to cut down my spending and I am going to the store, I take out some money from the bank and when it's gone, I have to go home. But I usually leave the store and lust after stuff I saw there and pretty soon I end up ordering them online.
I recently read that the way to develop willpower is to clench your muscles when you feel your resolve ebbing. I tried it with dessert and it somewhat works for that, but not so much for makeup. But look at it this way, your passion could be for something a lot less innocuous than makeup.