If I had to choose the most indispensable character trait to possess, it would be a toss-up between courage and perseverance. I say that because if you lack either virtue, you won’t be able to execute upon any of the others. Except for those born naturally talented into an environment in which those talents are catered to, I cannot think of any self-made man who lacked both of these character traits.
On perseverance, you have probably encountered this excellent Calvin Coolidge quote:
“Nothing in this world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan Press On! has solved and always will solve the problems of the human race.”