An excerpt from The Mind: Its Projections and Multiple Facets by Yogi Bhajan (page 41)
This connection between the mind and the tattvas leads to several common phenomena. All missionary people, all healers, and people who are zealous to help others get burned out. Counselors and advisors drain themselves, and it is a recognized professional hazard. Why? Because your mind gets involved and locked into the other person. It is called taking on the vibration of the other person.