What would make affirm an ever negating person?

Descartes negated "everything" ~ unto the realization that "I am negating;" thus he could not negate the "I am" of his "I am negating," hence "he am." The "affirmer" or "positer" of "there is nothing" therefore learns from Descartes that he or she is negating, hence he or she "is": ~ "I negate, therefore I am." Further down the philosophy chain, early Camus affirmed or posited (ahem) "suicide [self-murder] is the one truly serious [adolescent] philosophical problem." This is an example of "mind at the end of its human tether," aka "mortal mindedness," aka "self-hatred" (what Spielrein and Freud termed "death drives"), and many philosophers have resolved this typically generationally occurring existential psychologism. For example, Jules Lachelier moved past Schopenhauer and even 5-sense kantianism: "Being, as we conceive it, is not first a blind necessity, then a will, which is a priori enclosed by [categories of] perception, which [then becomes an existential] freedom."

A logical note: persistent negation is a circular pattern ("not this, not that" a la Gautama Buddha's teaching re "this mortal mindedness, this materialism") which may be virtuous (levels of nirvana and Buddhahood) or vicious. If one is self-hating, that is a dysfunctional psychologism; seek counseling/religious guidance/psychology: https://en.wikipedia.org/wiki/Maslow's_hierarchy_o... http://www.betterhelp.com/start A humorous example of the latter or vicious circularism of negation ("Just say 'no'?"): https://www.youtube.com/watch?v=4v3etuIw-aM

if things did not exist, it is impossible to negate them.

the meaning are inherent as in

opposite: being the other of a pair that are correspondingly complementary.

existence-nonexistence, life-death, gain-loss. happy-sad. wealthy-poor. educated-ignorant. sick-healthy.

so, in the end, "denialism" is affirming the self, much as nihilism is life-affirming.

Yes. Read Descartes's "Discourse on the Method." He makes a detailed argument as to why "I am not" cannot be a true statement.

Your death would cease that for sure.

Question not understood.

Denying the truth does not negate the truth. For example, it is true you will eventually die. While you can deny it, that won't change anything. In fact, death will prevent you from further negation. Other than that, threat of bodily harm or some other personal loss might cause you to hum a different tune.