What Is Up With The Term "Dark Night of the Soul" ?

We hear the term "Dark Night of the Soul" a lot when some souls describe certain periods of their life. Why use that term and does it cover and do we use it broadly to describe a period of time in our lives when we are separated from our very own souls? When we feel that separation, does it take out the self accounting we need to heal through all that we have chosen to do, or is it just another word for mistake? Are there mistakes or periods of "Dark Night of the Soul" ? Tune in and Join the Conversation, Friday Morning at 5:30 AM, PST! :)