I have a found an amazing drug that takes my mood from bad to good, from good to great and from great to ecstasy. The best news is that not only is this drug legal--it's free--and as far as I can tell, this drug has no ill side effects whatsoever.

My name is Dave, and I'm addicted to gratitude.

My journey to addiction began when I interviewed leaders such as Belfor CEO Sheldon Yellen and former Chessick Restaurant.com CEO Cary Chessick, for my last book. They didn't just talk about the power of gratitude, they practiced it in their lives, daily.

It continued when I worked very closely with Andy Cohen, my entrepreneur friend who has built an entire real-estate organization on gratitude and acts of service. And I met Charles Best, the founder of an amazing nonprofit Donors Choose, which was actually able to quantify the ROI of gratitude in a controlled study.

Like any addiction, mine began by establishing small habits. I began by writing one thank-you card per week. Today, I write three thank-you cards every morning on the train ride to work.

Happiness expert Shawn Acher taught me about the power of listing three things I'm grateful for every morning, and I began to do that. Columbia business school professor Srikumar Rao shared the power of listing five things I'm grateful for before I go to sleep at night, and now I do that.

A few weeks ago, we lost a major partner, who terminated a contract with us. I was feeling really down the next morning, not in a mood to write my thank-you cards. I pushed forward, and as I completed my third card, felt much better and more hopeful. It's actually physiologically impossible to feel gratitude and anger or sadness at the same time.

Last week I was running on the treadmill at home, and around mile six, I began to feel exhausted. I was done but was hoping to run seven miles. So for the next 10 minutes, I began to say out loud all of the things and people I'm grateful for. At 150 people, I had completed my goal of seven miles.

Recently another parent in our town said something inappropriate to my child. I immediately felt rage for this man and sadness about the situation. A year ago, I would have held on to those emotions.

Yesterday, I immediately shifted my feelings to gratitude, that my wife and I are parents who think very carefully about how we talk to our children and other children. And I immediately felt much better.

I begin and close team meetings with a moment of gratitude, and our company is more productive than ever. Since I've been writing and speaking about handwritten thank you cards for awhile now, I usually receive a couple per day in the mail, which leads to even more gratitude.

But the biggest difference gratitude has made on my life is on my happiness. I used to believe I could never be happy--no matter what, I was always driven for more. More revenues, more companies, more books, more children. I actually believed that my lack of contentment was good--because it kept me ambitious and striving for more.

Now, I feel the opposite way--now I believe I can always be happy, because no matter what, I have so much to be grateful for. I can still be driven to succeed, and happy at the same time, and it feels amazing.

I've become addicted to the feeling of authentic gratitude, and I'm not afraid to share it. It fills my day, and for the first time ever in my life, I can say that I'm very happy.

Anyone want a hit of gratitude?