How long can you keep a secret?

If you need to keep a big secret, here's a tip: Invent an alternate story to tell, and tell it so often that you believe it yourself.

That's one of the strategies identified by author Jane Isay, who lived for years with a whopper of a secret: that her husband was gay. The couple kept the truth from family, friends — even from their own children.

The toll that a years-long deception can take led Isay to write a book, "Secrets and Lies: Surviving the Truths That Change Our Lives," in which she chronicles what happened when her husband of 15 years told her the truth about his sexuality.

Through experience and research, Isay has learned why brain science argues against the ability to balance a secret and an open life at the same time.