Some 1 in 5 Americans treat their retirement account like a savings account to draw on at will. Certain 401(k) plans even offer a debit card option for you to borrow against your future. Not a good idea!

When you take a loan against your 401(k), you must pay back a pre-tax account with after-tax dollars. And then when you retire, the money is taxed again! So you're setting yourself up to be taxed twice on the same dollar.

But the big cost here is an opportunity one. If the money's not there, it has no chance to grow and multiply over the years.

Some people just accept they won't be able to ever retire. That's a choice and there's nothing wrong with it. But most people want to be able to retire at some point and have leisure time. Borrowing against your retirement plan is a sure way to sabotage your future.

Clark loves the Chilean approach to saving for retirement. The citizens of that country have personal mandatory accounts where 10% of their money is automatically taken each pay period and placed into a retirement account.

Remember, Social Security is really just an IOU from the government -- one that is unlikely to pan out for those in their 30s. Speaking of younger folks, when you change jobs, don't cash out your 401(k) and spend it. Roll it over to your new employer's plan!