I was reading through this thread and noticed this part; I feel I should clarify this misinterpretation of St. John’s work.
In this passage, he is talking about the Dark Night of the Senses, where God denies the soul certain consolations of the senses (the warm fuzziness you get when praying) so that they do not rely on the feeling they get out of prayer and so their desire for God grows. It is necessary during this time to also deny self will.
It would be in contradiction to the teachings of the saints to promote emptying your mind for meditation (centering prayer). Centering prayer, the kind of meditation used in Yoga, is dangerous and many Popes and even Catholic Answers have made comments on it in the negative.
In my personal opinion, often we forget that the Devil will find any way whatsoever to deter us away from God. Anything that has roots in a false religion has its purpose to lead us away from God and is therefore a great tool for Satan. Just like certain music or poses are consecrated to God (Gregorian chant, sign of the cross, genuflection, etc.) certain things have a special standing with Satan. Whatever doesn’t lead us to God should be cast away because this world is only a pit stop.