I have a debit card and I dont think I can go over zero in my spending. Pretty sure of it, because ATM refused me at one point when I had a very little on my account.

Plus, they allow me to get limits for spending. I would have to go to bank to withdraw more.

Also remainding myself materialism is why our society is decaying helps. I mostly "splurge" at Vietnamese markets and it's hard to spend that much when the skirts cost 10 euro and eyeshadows 2 euro. Sure, I have lots of skirts and make up, but... well, it's cheap stuff.
I mostly spend on travelling (going to places with great exchange rate helps, who needs London when there is Albania and Ukraine...) and lately on my activism and all that.