I’m a huge “Game of Thrones” fan. The show’s a little cheesy, but it contains real insights on everything from leadership to psychology to strategic planning. (Yes, I realize that the statement “I watch ‘Game of Thrones’ for the strategic planning,” is a pretty tough sell.)

Nevertheless, a powerful scene from a recent episode has stuck with me and I find myself thinking about the message it contains for businesses as well as for life.

GOT takes place on a continent divided by an ancient, massive wall that protects the somewhat brutal people on one side from the completely brutal people on the other. The wall is manned by a group of men called the Night’s Watch who take vows for life when they join.

Eventually, the cruelest tribes band together and form a huge army to breach the wall and lay waste to the lands behind it. The Night’s Watch is hopelessly outnumbered and terrified. In the scene that really affected me, six men have been instructed to hold the gate no matter what, and we see them staring in panic as a massive show of force runs down a tunnel toward them. Shakily, they raise their weapons, but there’s almost no point. Then one of the men begins to recite his vows.

Night gathers, and now my watch begins. It shall not end until my death. ... The others join him, their voices slowly gaining strength. I shall live and die at my post. I am the sword in the darkness, … Almost time to fight now. … the shield that guards the realms of men. I pledge my life and honor to the Night’s Watch, for this night and all the nights to come.

They’re ready, standing proudly with warriors’ adrenaline pumping through their veins. The camera cuts away just as the battle begins and even though it costs their lives, that small group successfully holds the gate, thereby allowing the entire wall to remain intact.

It was the saying of that vow that gave them the courage to fight, and in thinking about it, I realized that those words functioned for them the way a mission statement should function for a company.

A great mission statement is clear, specific, has a touch of originality and inspires every employee to be their best self. In moments of indecision, it should help illuminate the right path. Everyone should know it by heart and it should be prominently displayed internally as well as on customer-facing materials.

And while a company’s mission statement hopefully will never become a matter of life and death, it could help draw the bright line between success and failure.