The question stops being Can I afford this? You can likely afford lots of things if you have the cash on hand, but that’s not the point. You’re now asking yourself, “Does this move me closer to my goal(s)?” You’re considering the future ramifications of your decision in a very concrete way, and spending becomes about real trade-offs: “If I buy these shoes now, it will take me an extra month to hit my vacation goal.” You’ll quickly find that, when looking at your spending through this lens, you make great decisions!
