This quote is from Money, Possessions and Eternity by Randy Alcorn. I hope I always remember this lesson!
Practical Guidelines to Control Spending.
"Understand the difference between spending money and saving money.
Saving money is setting aside money for a future purpose. Money that is saved stays in your wallet or the bank and can be used for other purposes, including your needs or the needs of others that arise. On the other hand, money that is spent leaves your hands and is no longer at your disposal. Hence, when you buy a fifty-five dollar sweater for thrifty-five dollars, you do not save twenty dollars - you spend thirty-five dollars. Whether the sweater was worth thirty-five, fifty-five or two hundred dollars is irrelevant. The point is, the thrifty-five dollars is gone, and you have saved nothing. The next time you hear of a great sale on something you don't need, remember- if you keep 'saving' like this you will soon be broke!"