People can insert thoughts into your mind. This is more dangerous for psychic people. Use concentration exercises and read to combat this; boredom is an easy way to be drained.
Frederick LenzNirvikalpa samadhi is another matter. In order to enter into nirvikalpa samadhi, you must have a great deal of humility.
Frederick LenzPart of what we seek in Buddhism is the sense of quiet observation. We don't get so involved in a state of mind that we forget that it's just another transient state of mind, no matter how much ecstasy or agony is involved.
Frederick Lenz