Some of us grew up thinking that we only confess willful sin, since other “so-called sins” were unintentional.  One thing that should change our mind on this is the OT itself.  There were no sacrifices in the OT for willful sin, only unintentional sin.  These were the ones that when one discovered later, through reflection or reproof that he had not acted according to the law, then he would bring a sacrifice, which was confessional.  How often have I discovered, in hindsight, that I sinned against the royal law of love!  It is painful to see!  It is necessary to confess!

“Let those that do not call them (i.e. shortcoming and mistakes) sins, never think that themselves or any other persons are in such a state as that they can stand before infinite justice without a Mediator…The best of men still need Christ in his priestly office, to atone for their omissions, their short-comings,…their mistakes in judgment and practice, and their defects of various kinds.” John Wesley