Marrying for richer rather than poorer

Finally, workers often neglect to update their beneficiary information on their retirement accounts. As that's likely the biggest pot of money most people own, slipping up on that detail can be incredibly costly.

"With retirement accounts, if they go through the estate or even if someone makes the mistake of naming their estate as their beneficiary, you get a lot less tax deferral. So it is very important to be proactive and put your spouse as the beneficiary," says Weisman.

And if marital bliss doesn't last forever, don't forget to update beneficiaries right after a divorce. Nothing will sabotage your wealth-building efforts in life more than inadvertently giving the bulk of your estate to your ex after your death.