More thoughts on the above. This seems logical. The same spirits advised against doing channeling too frequently, and also against seeking physical proofs. Good advice, in any case. Aikido techniques of finding one's center, lowering the center of mass, and floating, help to relax one.
Tension brings the body in conflict with the mind.
Moreover, tension is a symptom of worse problems, like fear. Lack of EM interference. TV sets probably don't help, either. If possible, get away from dark and nasty areas. Of course, one must be able to pray in any situation, but if one is too influenced by a place, leaving would help.