Many of the qualities that come so effortlessly to dogs - loyalty, devotion, selflessness, unflagging optimism, unqualified love - can be elusive to humans.

If you still think you're a young pup then you are, no matter what the calendar says

A person can learn a lot from a dog, even a loopy one like ours. Marley taught me about living each day with unbridled exuberance and joy, about seizing the moment and following your heart. He taught me to appreciate the simple things-a walk in the woods, a fresh snowfall, a nap in a shaft of winter sunlight. And as he grew old and achy, he taught me about optimism in the face of adversity. Mostly, he taught me about friendship and selflessness and, above all else, unwavering loyalty.

Dogs are a really amazing eye opener for us humans because their lives are compressed into such a short period, so we can see them go from puppyhood to adolescence to strong adulthood and then into their sunset years in 10 to 12 years. It really drives home the point of how finite all our lives are.

When I wrote 'Marley & Me,' I had a clear audience in mind. And it did not include children. I wrote my book for adults and assumed only adults, and possibly teenagers, would be drawn to it.

Cats will outsmart dogs every time.

A dog doesn't care if you are rich or poor, educated of illiterate, clever or dull. Give him your heart and he will give you his. It was really quite simple, and yet we humans, so much wiser and more sophisticated, have always had trouble figuring out what really counts and what does not.