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Sloth represents laziness, and laziness is not a good trait in investing.
"Most investors don't spend enough time on their retirement planning and don't review their options sufficiently enough," Luxenberg says.
You have to do your homework, know your options and determine which are best, he says. "When to draw from retirement accounts, how to invest, what investment vehicles to use -- all have tax implications, for example," Luxenberg says.
Once you have a plan in place, it's important to stay on top of your investments through your retirement years.