Blaspheme is forgivable. Blaspheme of the Spirit is not.
Jesus in Mark 3:28-29

Important to know the difference!

All sin is equally forgivable by God through Christ. But, not all persons are ready/able to receive forgiveness. Some are in danger of their hearts becoming so hardened that they are resistant to forgiveness (ie. blaspheming the Spirit).

These are the person Jesus has uncomfortable words for in Mark 3 about being responsible for their eternal sin (actions which are unforgiven not because God won't forgive but because the individual refuses to receive).

1) "His" (Jesus) people who had an experience with Jesus back in the past and have not grown in grace since.

2) Religious people who worship their certainty rather than the person who is the Truth.

3) Family members who rely on faith of their parents, grandparents, friend, and others, instead of owning their own faith.