Well, I'm religious myself so maybe I'm coming at this from the wrong angle -- but I think most people who are happy have some kind of spiritual beliefs. Or maybe spiritual is not the right word, but they have beliefs about why life happens and what good they can do whilst they live it, and they feel a sense of connection to the world/universe and other people. That doesn't have to come in the form of organized religion.

And incidentally, I'm not offended and I can't imagine any reasonable person who would be offended by what you said. Not believing in a certain religion is your own personal choice.