What stopped you from becoming an astronaut?

A bad case of missile toe

I'm afraid of heights

Phobias, heights and being closed in.
Also not sure if this quote from Armageddon was requoting somebody who said it in life:
"You know we're sitting on four million pounds of fuel, one nuclear weapon and a thing that has 270,000 moving parts built by the lowest bidder. Makes you feel good, doesn't it?"

Knowing that no one has ever been in space.

Flat Earth :)

Not enough space

Unflattering Outfits

I quit taking up space in school.

Too much space between my ears!

the whole "rockets are unreliable and dangerous" thing, with a slice of realizing that being an astronaut is basically being a labourer in space

Because I was like accounting is definitely more interesting than space stuff O.o

My love for earth

Lack of opportunities in the 1970's. End of Apollo program.

I don’t like places with no atmosphere

Too much on planet earth to discover yet.

Gravity

My fear of space.

My aspirations, I guess

Fear of death.

Bad vision

School

Unfortunately, I did.

lack of interest