They removed an important word in the quote from the original - the phrase isnt "do the hardest thing", the original quote was "do the hardest thing possible"
The addition of that last word is the difference between the chance at eventual success and the human burning out on world peace, time machines, free energy devices.
naw but this kind of mindset ended up burning me out at times; some of us clearly take general ideas like this in different ways than intended perhaps
but I think the actual "trick" here is about finding unfilled niches rather than necessarily doing "the hardest thing"