I am "Jewish By Choice". The reason? Throughout my life if I cease to
seek a spiritual life, it is the same as when I eat only sugar for a few
weeks. I become "sick". I don't feel any joy in my life. I can find
short bouts of happiness, but even minor set backs affect me in a major way.
When I read the Torah or commentaries by the Fathers, I am refreshed, I
feel good, even major setbacks affect me only momentarily.
I do know people who do not feel the need for a spiritual life. I don't
know why they don't have the need. I only know I do.