Landing your first job, and the consistent paycheck that comes with it, is exciting.

After all, "The money you make can provide you freedom for life," co-founder of AE Wealth Management and best-selling author David Bach tells CNBC Make It, "but only if you spend less than you make."

That's why, as soon as you start making money, "the first thing you need to do is pay yourself first," he says, adding: It's "the single most important decision you will make when you get your first job."

Paying yourself first means that, whenever you earn money, you set aside a portion for your future self by putting it in a retirement account, where it can grow over time.