There are so many reasons to be honest in life, it's difficult to conceive of a time when honesty would not be the best policy except if the lies are white and, of course, at work. (I'm writing this with a smile so please no one take offense!)
Lying is part of human nature and we all do it, all the time. From answering our beloved's endless questions about his or her appearance or demeanor to telling our children Santa exists, we just lie as a matter of course and truly, it is often the kindest course of action one could take.
So the lies I have a problem with are the big ones, like, for example, theft, tax evasion, forgery, adultery, that sort of thing. While many of us never consider ourselves capable of these types of deep level lies and holding onto major secrets, some of us find ourselves in circumstances which cause snowballs to roll, leaving us buried under a mountain of cold, heartless untruths, and paying a very steep price indeed.
What is the price of secrecy?
For one thing, your very identity is at stake. For those people, like Arnold Schwarzenegger, who have undoubtedly been living some sort of double life for years and years, "who he is" is no longer a solid concept. He certainly can't claim to have been only Maria's husband or only Maria's children's father. Maria and his children no longer know, really, who he is or what his inner life is really like.
So identity, being known for who you are, being consistent in your life, that is at stake.
Then there's a little thing called trust. How can you expect anyone to really, deeply trust you if you are holding secrets from them? The transparency of any relationship (between adults, I should clarify) is what adds fertilizer and fuel to the roots and branches allowing it to grow. If there are secrets, there is no real growth; one person is holding back and not fully invested.
Finally, mental and emotional health can suffer profoundly from holding onto secrets. Of course not all secrets can or should be shared; but the hope is that you can find some peace in your life by not creating the dynamic that will foster secrets in the first place.