I have no experience with Byron Katie, but I've read Eckhart Tolle's "The Power of Now" and "Stillness Speaks."
I found the ideas to be inspiring and refreshing at the time. But as with all self-help I've tried, they never stuck, although they did help get me interested in spirituality enough to find a legit meditation hall.
I think Tolle's ideas mig
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"Cults," Sects, and "New Religious Movements"