Not taking full advantage of tax breaks
A person's actual investments can be less important than the types of accounts used for retirement investing.
The tax-favorable 401(k) plans and individual retirement accounts, or IRAs, are a huge leg up in getting to retirement because they enable your tax-deferred earnings to compound.
It's unwise to pass up the opportunity to invest in a plan when your employer matches a portion of your contributions. That's because you're passing up free money -- the equivalent of refusing a salary increase when it's offered.