The 46-year-old actor -whose girlfriend Jennifer Syme died in a car accident in 2001, two years after giving birth to the couple`s stillborn daughter Ava - penned `Ode To Happiness` after his pal Janey Bergam found his "self-pity" hilarious.
He explained: "I was in my kitchen hanging out with my friend Janey, and the radio was on - and this station was playing, like, an orgy of depressing, self-pitying, nostalgic music. You know, `I`m just so lonely and I`ve been left and my heart is broke.` It was so voluptuously horrible.
"And I just started to write on this piece of paper, because I had this image of, you know, the moment when you take a bath, you light that candle, and you`re really just kind of depressed. And it was making Janey laugh so hard, I just l kept going, piling on the self-pity."
Fans worried about the `47 Ronin` actor`s state of mind after he was photographed sitting morosely on a bench alone last year and even set up a global Cheer Up Keanu Day for June 15 but the actor merely found the concern "funny".
When asked about the campaign, he told the Guardian online: "Oh, the internet deal. It was brought to my attention. Yeah, it was funny. But no, the book predates that by a long time. We finished it in August 2009. It is hopefully, in a quiet and enjoyable way, transformative. The kind of thing that takes you from this one place to another - to look at yourself and, y`know, it can always be worse. I hate that sentence: of course it can always be worse!"