Hi -- I found this explaination to your question on RaptureReady.com.
In Matthew 12, we read that Jesus healed a man of demon possession. The Pharisees, who witnessed this miracle, in essence said that Jesus was able to cast out the demon because He was the ruler of demons. Jesus' reply to them was that they blasphemed the Holy Spirit, for which they could never be forgiven. In other words, by making that statement, they forfeited any further opportunity to receive God's gift of forgiveness and eternal life. To understand what it means to blaspheme the Holy Spirit, it is important to understand the sin in its context.
In Jesus' ministry, his staunchest opponents were the religious leaders of His day. They were called the Pharisees. The Pharisees were not ignorant of the Old Testament Scriptures. In fact, when King Herod sent for them to inquire where the Messiah was to be born, they immediately quoted the exact passage from Micah 5:2 that foretold His birth in Bethlehem (Matthew 1). Therefore, the Pharisees, with their knowledge of the Old Testament, should have been the first to recognize Jesus for who he was: the Son of God, the Messiah. However, they were proud and self-righteous people who believed that they were saved by keeping the Law and doing good works. Jesus preached that everyone was a sinner who needed to be saved by faith. This set Him against them because He preached a message contrary to what they taught the people.
It is important to understand that this was not a one-time rejection of Jesus Christ, nor was it done in ignorance. The Pharisees knew the prophecies about their Messiah. They were eyewitnesses to Jesus fulfilling them. They stood in the very presence of God incarnate and witnessed miracles that had never been performed in Israel before. However, instead of accepting Him as the Messiah and their Savior from sin, they set out on a campaign to reject Him because their pride got in their way. When Jesus charged them with blaspheming the Holy Spirit, a period of several months or more had elapsed in Jesus' ministry in which they repeatedly, consciously, and deliberately rejected Christ against solid evidence. In addition, they used their influence as religious leaders to attempt to keep others from accepting Christ. I believe that Jesus charged them with blaspheming the Holy Spirit because He saw that their hearts were so hard and determined to reject Him that this statement gave evidence that they would never repent. He even used an illustration in this same passage to show how their statement was so foolishly hostile toward Him that it defied logic. How can someone know that he or she has blasphemed the Holy Spirit? I believe that the person who is guilty of this sin will not even realize it in this life. Jesus said that Holy Spirit will "convict the world of sin, of righteousness and judgment" (Jn. 16:8-9).
Therefore, I believe that those who blaspheme the Holy Spirit are those who consciously and perhaps repeatedly reject Jesus Christ as their Lord and Savior by faith, and that they will not even be concerned about it. On the contrary, I find that those who have worried about being guilty of this sin are the ones who already received Christ and are saved who are under satanic attack to destroy their confidence. Or they are those who genuinely want to receive Christ but are afraid that God will not receive them. The point is this: If you are fearful of God's judgment for your sins, and you genuinely desire to have Jesus Christ by faith, then you can be assured that God is doing that in your life in order to bring you to faith in Christ. Therefore, you have not blasphemed the Spirit. Jesus said in John 6 that no one can come to Him unless God the Father draws them to Him. If you truly want Jesus as your Lord and Savior by faith, then you can be assured that God has not given up on you. Jesus said, "All that the Father gives to Me will come to Me, and the one who comes to Me I will certainly not drive away" (Jn. 6).
Exactly what I believe. Hope it helps.
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them