There seems to be a wide misunderstanding about this topic. People will refer to it also as 'denying' the Holy Spirit; but that is not that case. Matthew 12:31-32, Jesus said "Every sin and blasphemy can be forgiven, except sin and blasphemy against the Holy Spirit. This will never be forgiven." He goes on to say that if we blaspheme the Son Of Man, we will be forgiven, but not if we blaspheme His spiritual essence.
From this we can draw that there is a difference between denial and blasphemy. God is not going to reject everybody who was at one point an atheist. That is just the grace of God. We will be dead in our transgressions every day, and every day, God will make us alive through Christ.
There is only one state of complete godlessness in this life; this is only after blaspheming the Holy Spirit. However I have heard of situations wherein people frantically worry that they have committed the unforgivable sin. To this person I can say: take comfort. Your worry and guilt is indicative that God has called you to repentance. God would not do such a thing if He did not mean to forgive you.
But I have committed the sin! Why would God forgive me? Consider the latitude behind the words when you said them. You can state "I am hungry," and not be hungry. You can make a statement without thinking it through. There is no reason to believe that such a statement will cause eternal damnation. Did you truly mean it as you said it, or did you immediately regret it?
Using your peripherals:
From the corner of your eye, you can think you see a snake in a sock. You can see your mother in a stranger. The thing about these visions is at the time, you do believe them. Then you actually look and realize the truth. Most people who boldly claim that the Holy Spirit is evil have absolutely no understanding of the Spirit. If in your rebellious youth, you blasphemed the Spirit, such an action will not be held against you. You are still in the realm of forgiveness.
We cannot look from afar at those in God's hand and make a judgment, then be damned solely on that judgment. However if we are within the hand of God, and say after regret-less premeditation, "Hey, this is an evil hand!" then the hand will abandon us.
Just remember: if you want to be forgiven, then God has called you to repentance. God would not do that if you were beyond repentance. Pray honestly and you will be forgiven.
To read more of my articles, go to my Christian Articles section by clicking here