Hubris is dangerous overconfidence. In Greek stories it always gets punished.
In Greek tragedy, hubris was the pride that made a mortal act like a god. It always ended badly. Icarus flew too close to the sun on wax wings; they melted.
Telling everyone the Cowboys are definitely winning the Super Bowl in August. Hubris.
'We don't need to test it, it'll work' is startup hubris. Ship small, check, then grow.
Practice it in Skepsis