When Mike Pierce trained in a deep freezer for an 1,800 km marathon across Antarctica, he was attempting to follow in the footsteps of Ernest Shackleton, an explorer who led a wild, star-crossed expedition to the icy continent in 1914.

Pierce was first attracted to Shackleton's story, which he tells vividly, while browsing in a bookstore in Bakersfield, California. Before he knew it, he was completely absorbed, and a total stranger advised him to go to Antarctica himself for a taste of reality.

"The more you struggle," the stranger told him, "the more you walk in the shoes of your heroes."

Shackleton was a multi-dimensional character. Some criticized him for seeking wealth and attention and risking people's lives in the process, but he was also a fierce and heroic explorer whose leadership was legendary. Legend has it that 5,000 people responded to an ad Shackleton is said to have placed before the expedition:

Men wanted for hazardous journey. Low wages, bitter cold, long hours of complete darkness. Safe return doubtful. Honor and recognition in event of success.

Most of us won't go to Antarctica, so here's what I learned from Mike Pierce's keynote delivered at a conference in Memphis last week:

1. Focus on what you can control and let the rest go. When their ship, Endurance, got stuck in the ice, the crew got out and started to cut through six feet of ice by hand. Actual footage of this attempt exists. Shackleton allowed this to continue for awhile, until he told them to put the saws down and play a game. He realized that the biggest threat to his people wasn't physical, Pierce said, but mental. Cutting through the ice was not only futile, but demoralizing. It might feel like playing a game is the last thing you should do when your metaphorical ship is stuck, but for the sake of your team's well-being, that might just be what they need. "They had no control over the ship," Pierce said, "but they had full control of the game."

2. Do what you say you're going to do. After 497 days, the crew finally landed in a 23-foot dinghy, with no idea where they'd ended up after abandoning the shattered Endurance. Shackleton took five members of the crew and promised to return for the rest. In the world's roughest ocean, they faced off against waves of up to fifty feet. Books have been written about these 17 days. Shackleton and two crew members walked over 5,000 foot mountain peaks, knowing that they'd left 22 people 800 miles away. Amazingly, they went back for the ones they left behind, and everyone survived the expedition.

3. Redefine your level of difficulty. When Mike Pierce went to compete in the marathon in Antarctica, he was told that if the weather changed, he would find himself running for hours without knowing the difference between the sky and land. It would be impossible, in these circumstances, to tell whether he had made any progress at all. His many hours, weeks and months of practicing in a freezer helped, but couldn't fully prepare him for this experience. "To be more agile," he said, "we've got to change our definition of difficulty. I made the practice more difficult. It sounds insane, but I did it by design."