This is something that changed my life, and could change yours.
But let me tell you the story.
Most mornings I take the bus from my flat in Chelsea to go to work. The others I walk, because walking is good for getting ideas.
The bus drivers vary. Some are miserable buggers, losing no opportunity to pretend they didn't see you at the stop and sail past, or ignoring you when you get on.
But one shines out like a good deed in a naughty world. He gives a cheery good morning to everyone, and they respond. He gives smiles and gets smiles back.
He may not be THE nicest bus driver in London, but he's the nicest one I see regularly. His name is Sacha Jovecic, so he must come from some part of what was Yugoslavia.
Laugh and the world laughs with you; weep and you weep alone is from a poem by Ella Wheeler. It is true.
When I was younger, especially when I was successful, I became unduly arrogant and snooty. Failure taught me a little humility. And I also developed the habit of smiling pretty much all the time no matter what.
The act of smiling makes me feel better. But it doesn't stop there. To start with, people smile back. Not just some people, but a very high proportion. And this has an almost miraculous effect. It makes you even happier yourself.
I apologise if this homespun wisdom is boring you. I can only say that it is one of the most valuable, and simplest, lessons I have ever learned.
If you've read this far you may be worried that I'll start flogging the joys of EADIM. You can relax. I won't. I'm going to talk a little more about happiness.
I have a good friend called Professor Srikumar Rao. He is famous. You can see him talking http://www.ted.com/talks/srikumar_rao_plug_into_your_hard_wired_happiness.html.
The other day I got him to come and let me interview him. We were talking about his new book, Happiness at Work: Be Resilient, Motivated, and Successful - No Matter What. I recommend it.
One interesting thing is that like me Srikumar speaks from experience. He told me that he spent years being miserable in his job: he was an executive at Warner Communications and McGraw-Hill before becoming Dean of the Marketing School at Long Island University, which is where we first met.
I am not getting a commission if you buy the book, by the way. I just think that happiness works - and the more happiness the better.
By the way: one small confession, Srikumar did speak at EADIM two years ago - but not this time.
Oh, and if you'd like to see the interview, let me know.