My mental trick to not buy things
Maybe this is dumb and I'm literally the only person who this is effective for, but I wanted to share a little trick I've picked up over the years to not buy things. I got to exercise this today as Apple's new HomeView is available, and I could get it delivered in a few hours. I put one in my bag, went to check out, and I was greeted with the above screen showing me the total.
My little trick is I pretend that the money is already spent and now the checkout page is giving me 2 options. I can either choose to have Apple give me the HomeView or they can give me $329.65. When I thought about it that way, it was immediately obvious to me that I'd rather have them give me $330 than a HomeView, so I didn't buy it.
Anyway, this probably isn't useful for most folks, but I've personally found it an effective way to stop myself from buying things that I don't actually want that much.