While teaching at the University of Pennsylvania, Dr. Tony Campolo once turned an ordinary lecture into an unforgettable lesson. He asked an unsuspecting student sitting in the front row, "Young man, how long have you lived?" The student answered his age. Tony responded, "No, no, no. That's how long your heart has been pumping blood. That's not how long you have lived."

Tony Campolo then told the class about one of the most memorable moments of his life. In 1944, his fourth-grade class took a field trip to the top of the Empire State Building. It was the tallest building in the world at the time. When nine-year-old Tony got off the elevator and stepped onto the observation deck overlooking New York City, time stood still. He said, "In one mystical, magical moment I took in the city. If I live a million years, that moment will still be part of my consciousness, because I was fully alive when I lived it."

Tony turned back to the student. "Now, let me ask you the question again. How long have you lived?” The student sheepishly said, “When you say it that way, maybe an hour; maybe a minute; maybe two minutes.”

According to psychologists Matthew Killingsworth and Daniel Gilbert, the average person spends 46.9 percent of their time thinking about something other than what they're doing in the present moment. We're half-present half the time, which means we're half-alive.