Dither no longer: It's never too early to learn how to catastrophize.
Children are like sponges. Selfish, vicious sponges. They are poised to soak up the fruits of your own knowledge of catastrophizing. My understanding is that sponges soak up fruit. Amazing creatures.
Their attitude and environment should already incline them toward catastrophizing. They can't have more treats. They can't not eat disgusting foods forced on them by their parents. They can't wake their parents up quickly enough during the night. Once they reach school age, they'll almost immediately either become a bully, in which case they'll be preoccupied with the flaws of others, or a bully's victim, in which case they'll be preoccupied with their own flaws.
All it takes to rear a catastrophizer, really, is a firm hand and a consistently negative attitude. "Is that a blemish? Oh, my mistake, I forgot you had a disfiguring birthmark there." "You did well on this multiplication test! There are so many professions you'll be able to choose from and be disappointed with!" "You failed your multiplication test! Not that it matters. You'll end up working in an office and feeling as though your talents are underutilized no matter what you score on some totally inconsequential quiz."
Whatever your concerns about catastrophic child-rearing, take heart: even if you somehow fail to instill in your child an affinity for catastrophizing, life will.