A version of this article originally appeared on CBS News Money Watch.

There were once two families that lived next to each other. One received a $2 million inheritance. They traveled, had a nice boat and gave to charity. They took calculated investment risks, and the risks paid off. They averaged an incredible 12 percent return on their money every year for 20 years.

The other family did well but wasn't nearly as successful. A good year for them amounted to $75,000 in income. They also took vacations and gave to charity, just not as nice or as much. Although they too took calculated investment risks, they earned a more earthly 8 percent average return over the same 20-year time horizon.

Both families have planned for retirement. One is financially secure. They have more than they need to continue to travel, spend winters in Palm Springs and lead their ideal retirement lifestyle. Unfortunately, the other family is in for hard times. The retirement they envisioned will not come to pass, and they may have to work 10 years more just to get by.

Common sense tells us the family that received the inheritance and had a 12 percent investment return for 20 years is the "successful" family, while the other family will experience financial problems during retirement. But guess what. Common sense is wrong.

It doesn't matter how much you make or whether or not you receive a windfall. What matters is how much you keep. There are a lot of sudden wealth recipients who spend down their windfall – the stats are alarming. A Sports Illustrated report titled "Why Athletes Go Broke" shows 78 percent of NFL players are bankrupt or facing serious financial stress within just two years of ending their playing careers and that 60 percent of NBA players are broke within five years of retiring from the game (the reason why athletes go broke may surprise you). And it's not just professional athletes who suddenly lose their sudden wealth. The rate of lottery winners filing for bankruptcy within five years of winning is double that of the general population, and 70 percent of families who inherit a significant amount of money lose control of their assets in the first generation following the bequest.

Too often we focus almost exclusively on managing our assets when we should be spending time building our assets and managing our liabilities. Earning a 10 percent investment return instead of an 8 percent investment return is less effective in providing you financial independence, a great lifestyle and a successful retirement than is controlling your expenses and saving. 

The best way to get and keep your finances on track is to automatically shift income into savings and investments each month as well as limiting those "one-time" purchases that continue to require money –  this is one of the seven deadly financial sins for those who win the lottery or receive an inheritance. Take into consideration not only the initial cost but all of the ongoing costs. By putting your savings plan on autopilot, limiting ongoing expenses, and doing some planning with a Certified Financial Planner™ professional, you can rest assured your assets and your liabilities will be managed appropriately.