Unforgivable Sin

One thing that has been bothering me for awhile now is the issue of the Unforgivable Sin (Blasphemy of the Holy Spirit). I have struggled with this before until someone explained it to me, but a couple of months ago, I read a post by this same someone telling someone else that they committed this sin for claiming that they saved souls.

I have been in a state of terror off and on since then. Even if the rebellious are eventually destroyed, I don't want to go where they're going.

I know I shouldn't base my faith off the idea of punishments and rewards. It's so hard not to do so, especially after being brought up Catholic and being sucked into a Fundie cult later on. The idea of being able to commit a sin that would guarantee that they are permantently doomed.

I'm terrified and sick. I don't know what to do. I don't even want to even think about the Holy Spirit for fear that I may screw up somehow.