Here's an example of how I use this idea of boundaries in my closet.
I have four shelves for sweaters that I cannot hang. If I find a sweater I want to buy, I need to make sure that it is better than what I have.
It keeps me reigned in when I shop, because let's face it-I can always find something cute when I scroll and I can always justify a price if it's on sale! I still fight against decades of shopping for fun, shopping when stressed, shopping when I wanted to feel cute.
Having that physical boundary helps me make more thoughtful choices, definitely helps me save money and I don't have a closet full of clothes crammed together(making it harder to keep clean and get ready!)