I don't know if there's a proper way to define toughness in a runner, but I do know that there comes a sudden moment when the mindset shifts. The impossible becomes doable, or at least attemptable. The long run goes from two miles to four to ten to fifteen, until it becomes routine at some point deep in an intense training cycle to knock off a couple hours without giving it a thought.
Home-based businesses are one of the fastest-growing segments in our economy, and that trend will only continue, as the age of the corporation, which began barely a century ago, now gives way to the age of the entrepreneur.