"Quite frankly, when in the midst of grief, whether it is related to the death of a loved one or the loss of a marriage, you are not in your right mind," she said. "Decisions that seem very sensible, in the distance of time are shown to be not so much."
Given the emotional consequences of finding yourself suddenly single, it's wise, whenever possible, to defer major decisions for six months to a year, according to advisors. Many newly widowed or divorced people feel compelled to make big changes at a time when their emotions are raw and stress levels high. "There is usually a compulsion to do something big—sell the house, go on that big trip—and very often that involves finances," explained Gibson.
Read MoreKeep emotion out of investing
One way to deal with the "noise in your head" if you are newly widowed or divorced, according to advisor Susan Bradley, is to do what Bradley calls a "brain dump." The exercise entails making a list, by keyword, of the issues and obligations you confront and then prioritizing the items by urgency.
"Find the one or two things that really need to be addressed now, such as paying taxes on time," she said.