The Grace Reading
The unpardonable sin has tortured more tender hearts than almost any verse in Scripture. People who love God lie awake wondering whether one dark thought, one word thrown in anger, one long season of doubt has locked them out forever. So take the fear off the table first: every one of your sins is forgiven, and the sin Jesus names here is not one a believer can stumble into.
Look at who is in the room. A few verses earlier a demon-possessed man who is blind and mute is brought to Jesus, and Jesus heals him by the Spirit of God (Matthew 12:22). The crowd starts asking whether this could be the Son of David, the Messiah. And the Pharisees, watching the Spirit of God work in front of their eyes, announce that He does it by Beelzebub, the ruler of the demons. That is the setting. Blasphemy against the Spirit is not a slip of the tongue. It is looking straight at the light and calling it darkness, with full knowledge, on purpose.
Jesus draws the line carefully. “Anyone who speaks a word against the Son of Man, it will be forgiven him.” Even the crowd that would soon shout for His crucifixion is not beyond mercy, and Acts 2 proves it, when thousands who had rejected Jesus the man changed their minds and were saved. But the settled, final rejection of the Spirit's testimony about Christ is different. It refuses the one remedy God has given. Not because God runs out of grace, but because the heart has slammed the only door grace comes through.
Here is the part that frees the anxious believer. If you belong to Christ, you were sealed with the Holy Spirit of promise (Ephesians 1:13). The Spirit is not visiting you; He lives in you. You cannot be indwelt by the Spirit and finally rejecting Him at the same time. Those two things cannot occupy the same heart.
Which means the very fear that you have committed this sin is the evidence that you have not. Dread of losing God is not the sound of a hardened heart. It is the Spirit still at work in you, still drawing, still testifying that Jesus is yours. A person who has truly rejected the Spirit feels no grief over it at all. Your grief is proof of life.
The Common Misreading
This verse gets used as a whip. A teacher tells a congregation that if they blaspheme the Spirit (sometimes defined as doubting, sometimes as walking away for a season, sometimes left menacingly vague), they may have forfeited salvation with no way back. Anxious people then spend years auditing their own thoughts for the unforgivable one. That is spiritual cruelty, and it misreads Jesus completely. He was not warning trembling followers; He was pronouncing a verdict over men who watched the Spirit heal and called it the work of the devil.
The question answers itself. If you are afraid you have committed the unpardonable sin, you have not, because fear of losing God is the Spirit's fingerprint, not the mark of a heart that has rejected Him. All your sins were carried at the cross. The Spirit who sealed you is not preparing to abandon you over the very anxiety He is soothing.