Enenekontenneaphobia

Enenekontenneaphobia (from Greek enenḗkonta, "ninety", and ennéa, "nine") is the fear of number 99. The nature of this fear is due to being one shy of the century mark. This fear often comes about due to the shyness in value, like achieving 99% in the video game but couldn't go any further, or even seeing a grandparent or great-grandparent dying at age 99. 99-year olds may commonly have this fear until they make it to 100.