In my opinion, one of the most “damaging” things we can tell our children, or ourselves for that matter, is that if we set our mind to it and have the perseverance we can do anything, accomplish anything, be anything. WRONG.
No matter how much I may want to be a nuclear physicist my brain simply will not grasp the finer, much less coarser, points of physics or math. No matter how much I might want to be a sumo wrestler, my body, dexterity and athletic ability forbids it.
So if I were going to talk to The Cat in the Hat I would tell him to change what he preaches to:
You have brains in your head
You have feet in your shoes
Try things, succeed OR fail,
You’ve got nothing to lose.