Musk's formulation carries a quiet stubbornness that distinguishes it from cheerier versions of persistence—notice he doesn't promise rewards or breakthroughs, only that you keep moving until circumstances literally stop you. There's almost a defiant realism here: most people quit when they *could* continue, surrendering to self-doubt or comfort before external forces demand it. Consider someone learning a difficult skill like woodworking; they'll abandon it at the first spoiled project, even though nothing has actually prevented further attempts—only their own discouragement has. His version suggests the boundary between courage and foolishness isn't about knowing when to quit, but rather waiting until the world itself decides for you.