Master Sheng Yen's Video Dharma Talks:
Is there any harm in entering meditative concentration?
It is not easy to enter concentration, and one who can attain concentration can certainly leave it, so there is no need to worry about not being able to come out of the state of meditative concentration. Extended concentration is an indication of good health, not a cause of physical problems. To avoid harmful hallucinatory states or so-called demonic states, practice under an experienced Buddhist teacher.
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