When I was 6, my dad taught me a critical money lesson that forever changed the way I spend

It was about 1997 when my dad first gave me the, Is that a want or a need? talk.

I was a kindergartner who really wanted chocolate milk at the Soda Shop, a local diner in my hometown of Davidson, North Carolina.

The speech went over my 6-year-old head, but the conclusion of the message stuck - never ask for chocolate milk at a restaurant.

Order water because it's free.

I learned that afternoon that chocolate milk qualifies as a want, while water qualifies as a need.

As I got older, I started to figure out how other things fall under these two categories. I learned, for example, that those new pair of Sambas I'd been eyeing counted as a want, but tennis shoes counted as a need, as I traveled for competitive tennis tournaments every weekend.

At first, I was guided by my dad and his definitions of "wants" and "needs," but eventually I started to formulate my own definitions. I noticed that the chocolate milk column grew exponentially quicker than the water column - luckily for childhood me, I knew not to dare touch the "want" column.

Sure, it was helpful to develop this frugal lifestyle centered around "need-buying" as a high schooler and college student, but my dad's lesson has become more valuable than ever upon entering the "real world," where in order to stay afloat with minimal income in an expensive city New York City, you have to distinguish needs and wants.

What this distinction does, is it makes you a diligent and conscious spender, a habit that takes time to form - a habit that a personal finance book or class can define, but can never truly teach.

That 1997 chocolate milk lesson looms over every purchase I make. I first determine whether or not I'm buying a want or a need, and if it's a want, I weigh the pros and cons before mindlessly spending.

Of course, there's always a time and place for a chocolate milk - the occasional splurge keeps you sane - but for the most part, I'll be the one with the glass of water.