I have found that for many couples, they put off coming into mediation because they are reluctant to admit publicly that their marriage is not longer good. I have heard “good” to be further detailed with these descriptors: viable, worthwhile, rewarding, healthy, etc.
Coming to a point of being able to delineate what “exactly” brings a couple to mediation is unnecessary. In the same way that no one puts demands on you to specify why you wanted to get married, your mediator has no expectation that you describe that which has led to your choice to divorce.
Of course, there are times when the couple wants to discuss those details. As each mediation is “of the couple,” those who want to open a discussion around the why behind their choice to separate are free to do so. But rest assured, I do not need to be convinced of the merits of the choice behind your entry into mediation. As self-actualized people making a significant life change, I trust that by the time you arrive, you have (by and large) come to terms with the choice and now are seeking out professional assistance on formalizing your decision . . . unless you change your minds and thereby your choice, because that can happen, too.
I trust you.