Many meditation teachers advise students to put serious effort into focusing attention on one object eg the breath, in order to stabilize awareness. Some Zen teachers state that one must achieve samadhi first before making any real progress in meditation practice. This forced mental effort goes hand-in-hand with forced physical effort, "breaking through barriers" of pain. Stable one-pointed awareness can indeed be achieved by some using this marine-style method. However, those who have some variant of attention-deficit disorder, and or low pain threshold, and all of us when we have a lot going on in our lives, are not marine material.
Hallmarks of samadhi include the end of "self-talk" (the obvious loud stuff at least) and complete physical ease of sitting (for prolonged periods). Both of these are major reliefs, so there's subtle euphoria, and the tendency to think "I've got it!" - delusion!! It's a small, very early step, in a lifelong journey.
What's not commonly appreciated, is that a self-induced hypnotic trance can easily be confused with samadhi. One can literally escape the prolonged mental and physical strain by going into a trance state. In trance, one feels "locked-in on target" (like a jet fighter's canon) on the focus of attention.
In the samadhi one cultivates with open-awareness meditation (Vipassana, Zen etc), one should be able to slowly move physically, look around, etc and REMAIN in samadhi. If doing these things ends the state ("breaks the spell"), it was self-hypnosis - a good hypnotist can help get you there in 10 minutes.
We are trying to wake up! Samadhi - fully conscious, awake and aware - is cultivated through dedicated skillful mindfulness practice that is unforced, but continuous throughout one's (initially) waking hours.
|Photo from Insight Meditation Society's website: http://www.dharma.org/|