I personally think that's why the more "active visualization" is much more effective, verses the "blanking out" state of mind, which in truth, leaves one open for other entity possession and disturbance. Anyone well versed in Spiritual warfare can attest to the necessity of protection techniques when entering these exercises and disciplines, both Spiritual and psychic (such as the golden or white light circles and shells or spheres of protection, angelic evocations, prayer, etc.).