I've always wondered why Sam Harris is mentioned so often at Reddit when people are talking about mindfulness instruction. Sam Harris is just parroting Jon Kabat-Zinn in the instruction. Harris even notes his source as Kabat-Zinn in this article. Kabat-Zinn's instructions are much more detailed. He has several books on the topic and was the head of the MBSR (mindfulness based stress reduction) program for decades. Kabat-Zinn's experience on the topic is much more broad-based than Sam Harris since Kabat-Zinn is the person who is credited as popularizing mindfulness in the US with a secular view. Your comment reminds me that the reason Reddit mentions Harris so much could be that Sam Harris is anti-theist while Jon Kabat-Zinn is secular. Reddit tends toward the anti-theist view.