What is poker dong for my well-being?

[lambethwalk]

I am 74 years old, mentally alert and very slightly disabled. I love playing holdem and spend at least 4 hours a day doing so. I am a pretty good player, playing low limit tournaments and I do not gamble. I have played poker all my life with a gap of 20 years between the age of 40 to 60.
My family are not in the least bit interested in the game and maintain that I am wasting my time. According to them, I am obsessed and could best be using my time by birdwatching or doing charitable work.
What can I say to them that will help them understand what it is that I am doing and why I'm doing it? In fact I would like to understand the why's and wherefor's of what I am doing.
Apart from any advice anyone can give me, perhaps I can be referred to a book or two that would help.
There is a certain degree of desperation in this plea for help.