Few things come to mind.
1. The situation with the pharisees was quite different. They were in a position to directly witness the power of God in Jesus's miracles, and they made a very public charge against Jesus's ministry of healing and exorcism. Not comparable to a momentary private thought.
2. Even then, it's far from clear to me from the text that even these pharisees had actually committed the kind of blasphemy against the Holy Spirit that Jesus referred to. It would perhaps make sense to think that Jesus was warning them rather than saying they had already committed it.
3. The power of Christ's atoning work is amazing beyond our comprehension. The idea that a momentary blasphemous
thought about the Holy Spirit would forever remove that from a person just seems very implausible. Especially because it seems rather common that people occasionally think all kinds of weird thoughts, and our thoughts don't even seem to be completely in our direct conscious control (see
Intrusive Thoughts (Wikipedia).
4. While emotions may be the spice of life in general, they are not any inerrant guide to our spiritual status. Expecting to always have the same kind of emotional reactions that can be used to gauge one's acceptance (or lack thereof) by God can be very tricky and needlessly anxiety-inducing.