Harshness and nihilism

I hope you will allow me to ask another question. We all know that there are many harsh statements in the Bible (Matthew 12:31-32, Hebrews 10). Sometimes, these harsh statements are along the lines of "If such and such a condition is fulfilled, then there is no hope left for such and such a person to whom the condition applies" - i.e. the implication is that such and such a person is doomed to hell. My question is: Sometimes, a given person does not even know if he or she has fulfilled one of those conditions. To my knowledge, people have tried to give explanations of these scenarios, but I do not know if there is a total, definitive, absolute, verdict, on what these conditions actually are that doom someone to hell without hope. In life, we usually do not know things with absolute certainty, and a certain amount of belief in positive outcomes of uncertain events is usually needed to preclude a descent into total nihilism. Colloquially, one might say that as long as a person believes there is light at the end of the tunnel, he or she would be able to pick himself or herself up the next day and make an attempt to continue walking with God. But if this person is faced with uncertainty over eternal salvation, can it trigger nihilism and despair? **Is there ever a situation (or can there be such a situation) where fear over damnation to hell due to the scenarios described led a person who need not have borne such fear, to descend to unnecessary nihilism and hence give up on Christianity with the attitude "well, since I am already condemned unconditionally, what is the point of seeking God any longer?"** (It is true that no one can really be sure of having been condemned unconditionally by the scenarios in Matthew 12 and Hebrews 10, but what if pessimism led the person to progress from the idea that he or she might have committed an unforgivable sin to a belief that he or she had committed it, with the resulting nihilism described above?)