many negative encounters spring from the overactive Swadhisthana center many people who complain of a negative attack during trance probably have developed the Swadhisthana center but neglected the higher energy centers its best to have them well balanced for a smooth projection.
Swadhisthana is the orange primary energy center for those that don't know.
(http://upload.wikimedia.org/wikipedia/commons/4/4b/Swadhisthana.png)