You're Spending Exclusively with Cards
Studies show that if you spend money with mostly plastic instead of paper, you're bound to spend more money because you're not really cognizant of how much you're spending and how much you have left. Okay, I didn't read this from a scientific study, but I read it in a Cosmo article which is basically just as legit. But essentially if you carry around $200 cash for the week as your allowance for spending money on necessities like groceries, MetroCards, etc., it's easier to monitor yourself than it is by mindlessly and eagerly swiping your AmEx. You'll inevitably save more by using mainly cash, and the only downside is by carrying around a lot of dollar bills, people might think you're a stripper.
[Photo via @americanexpress]