Rich-Easy Millionaire
I'm sure you've heard it said that compound interest is one of the most powerful concepts in the world; and it is. You're probably already familiar with the Rule of 72, but if not here goes.

If you divide the number 72 by an interest rate it will tell you how long it will take for you to double your money. This is so simple you can do it on a napkin and amaze your friends! For instance, over the past 70 years or so the S&P 500 has averaged almost 11% annually according to Towers Data. If we round that down to 10% then here's how the formula works: 72/10 = 7.2
So if you can earn 10% annually on your investments you'll double your money in 7.2 years.

Example:
Suppose you have $100,000, you're 35 years old, and you average the 10% after fees and expenses inside your tax-deferred retirement plan. You don't add another penny to it-ever. Here's approximately what would happen;*
35 = $100,000
42 = $200,000
49 = $400,000
56 = $800,000
63 = $1,600,000

Now, what if you added some additional money to your account every year, say $5,000?

35 = $100,000
42 = $247,051
49 = $533,612
56 = $1,092,039
63 = $2,180,254

*Calculations courtesy Raymond James Financial Planning Tools.
Of course this assumes you can earn 10% annually, which is not guaranteed. But it does go to show that if you could earn the 10% and added a modest amount to your $100,000 nest egg, you could wind up with a nice chunk of money down the road. Even without adding any more money the power of compound interest would make you a millionaire by around age 60 if you started with the $100,000 at age 35.

But as we know, money without the wisdom to manage it properly, can be a miserable burden. So make sure you invest as much of your time learning how to be a wise financial steward as you are learning how to accumulate it.