My understanding of the sin against the Spirit is rejection.
When we reject His teachings or ignore His guidance we allow ourselves to become numb to His presence. When we become numb to the point of having a hardened heart we disregard all signs, sounds, and correction of the Holy Spirit there bye trusting only in our own abilities and understanding. In other words we believe we don't need any savior, any guidance. And the Spirit will remove Himself from us leaving us completely alone. And alone there is no hope, only death through eternal separation of our life giver. And as it has been said (or written) if you are worrying as to whether or not you have committed this unpardonable sin, you haven't.
God Bless,
Brother Jerry