If there's anything that we humans want in life is to be happy. It's something we all crave, and it's the surest sign that we are truly successful in our lives and relationships. As Stanford researcher Emma Seppala noted in her book, The Happiness Track, "Happiness -- defined as a state of heightened positive emotion -- has a profound positive effect on our professional and personal lives."

In 1922, while Albert Einstein was traveling in Japan, he got some news that surely made him very happy: he had just been awarded the Nobel Prize in physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect." When this news became public, Einstein became an instant celebrity in Japan, with thousands of people crowding to see this famous man. In response to this overnight fame, Einstein holed up in a room at Tokyo's Imperial Hotel, trying to avoid the mobs.

At some point during his stay at the Imperial Hotel, a messenger knocked on Einstein's door with a delivery. Instead of giving the messenger a tip, Einstein scribbled out two notes, and then signed and gave them to him.

According to a Washington Post report, these two notes were auctioned off yesterday for a combined $1.8 million.

And what did Einstein write in these notes?

The first note (which sold for $1.56 million) reads:

"A calm and modest life brings more happiness than the pursuit of success combined with constant restlessness."

The second note (which sold for a much more modest $240,000) reads:

"When there's a will, there's a way."

Simple and sweet advice, a unified theory of happiness from one very happy Albert Einstein to a messenger -- and, ultimately, to the world.