Spoiler alert: If you haven't finished the video, I'm now going to ruin the surprise.

Several seconds into the film, a person in a gorilla suit walks into the frame, thumps his chest, and saunters off. The vast majority of people who are busy counting the white-shirt passes simply don't see the gorilla. Don't believe me? Try it on a friend.

Martha Beck is the author of The Four-Day Win (Rodale).

More Martha Beck

• How to deal with transition anxiety
• The cure for self-consciousness
• How to get the world to see the real you