For all his impressive success, Tesla Motors and SpaceX founder Elon Musk is no stranger to failure. In fact, he often revels in sharing his fails, which can involve spectacular explosions.

He's also seen his ventures face down imminent collapse, especially when the bottom fell out of the economy about a decade ago. But Tesla recovered to become one of the most valuable automakers and SpaceX is today an undeniable leader in commercial space-faring.

What inspires Musk to persevere time and again? Well, we know he's concerned about the impending energy and climate crises that confront humanity, hence his interest in renewable energy, zero-emission vehicles and moving us to Mars in case the planet can't be saved.

These concerns obviously motivate him, but what about the inspiration to continue on down such a long road filled with countless setbacks?

Turns out one surprising source is J.R.R. Tolkein's "The Lord of the Rings."

When one young student from India asked Musk via Twitter how the classic tome filled with hobbits, orcs, wizards and elves inspired him, the serial executive was quick to respond with his takeaway from the epic tale of adventure:

"Don't give up if the cause is important enough, even if you believe you are walking into doom. Good friends really matter."

In a way it's comforting to know that even billionaires often feel they're walking into oblivion, but Musk also knows the feeling of making it through to the other side, just like some certain hairy-footed heroes.

One does have to wonder what friends Elon leans on most to get through those dark times. Aren't most of us under the assumption he doesn't have time for friends? He must have watched those "Lord of the Rings" movies with someone, though...