It is a thought form, a belief system, a lie perhaps that you believe and that gets into your fields and begins to take over your psyche, just like a virus. Those are real. How do you invite these viruses in and make yourself your own worst enemy? The Codependent for example invites more psychic viruses in than many other Archetypes. Smudging will not do it in the long run. Go to your patterns. We learn this in our Shamanic Teacher Training here.