I don’t think you have to be religious about mindfulness by any means, but I do think it helps. For those of us who haven’t already crossed over into a timeless state where all of life is deep meditation, I think there is a mood that supports the practice in the sense that it helps to be “in the mood” to do it. Of course, it is critical to strengthen the practice by doing it even when one is not in the mood, but it is also possible to cultivate the mood, and that’s where religiousness can help.
I’m very carefully not saying what kind of religion helps, but obviously it would stand to reason that Buddhism has some things to offer. I use an alchemical combination of Buddhism and my native Judaism, and I think anybody with religious experience can probably find a place for mindfulness in their life. All that matters is that it’s a superstructure of mythic narrative that feels like it applies to you, whether you think of it as religious or not. The mechanism of action here is a story about who and what you are that gets you in the mood to meditate on it.
The story is not the point; the mood is the point. This is the kind of thing that gets me into hot water with more traditionally-minded people, and this is why my wife is going to be the rabbi, and I’m going to be leading the “alternative” meditation group in the little side chapel. But I’ll say it anyway: I think religion might be for regulating mood, and that’s very important! We can use this powerful technology of mythic place-finding for putting ourselves in an expansive, contemplative mood. In that mood, we can open to insight.