If you think that "something" is impossible to do... Give it to humans and they will make it "possible" -- Anon Guest
Never tell a Human what's impossible. -- Galactic Alliance saying.
They had once said that travelling faster than light was impossible, just like time travel. Humans managed to find one-way wormholes, which utilised both, and then proceeded to use them to seed their colonies all over surprising corners of space. Humans, it seemed, accomplished six impossible things before teatime.
It was impossible to hold one's own against the Vorax, unless you were a Human. It was impossible to merge conflicting technological philosophies of construction, unless you were a Human. It was impossible to terraform a rogue planet... unless you were a bunch of Humans who thought it worthwhile.