Interesting. Outside of bills I only use cash. This has several affects:

1) Never leave the house with more cash on you than you intend on spending that day / that trip. This automatically limits the amount you CAN spend. No more splurging or random "I think I need that" moments. Average day I keep only $20 in my pocket. Need gas? Remember to grab extra cash. Going shopping? Only grab what you plan on spending. Leave the rest at home or in your account.

2) You become VERY aware of how much things cost when you have to count out physical cash as opposed to just swiping a card. This has led me to put back items I might otherwise have bought and not used as much as I thought I would.

3) I never use change, only whole bills, even if I know I have that 9 cents in my pocket. When I get home I empty all the change into a jar. In 3-6 months i can easily save $200+ worth of change. Most banks allow you to cash it in without charging a fee.

Separate things I do:

Never get soda when eating out, only get free water -- you'll save anywhere from 1-3 bucks each time. If you buy lunch once per day 5 days a week that saves you anywhere from $20-60 per month, and is healthier for you!

Use coupons whenever possible.

Try to only buy grocery items that are on sale (but confirm that it's a real sales price and not an inflated sales price), or else buy generic instead.

(Those two things combined typically save me 25% or more on EVERY grocery receipt I have!)