The esoteric (hidden) meaning of metempsychosis.

The metempsychosis is only a series of training periods in the refuge heavens (called Zion by the Buddhists). From the highest Zion, Maitreya Buddha, the future savior, will descend to earth, and the Christian savior also comes from Zion. Marginalized groups and "outsiders" such as psychiatric patients are often misunderstood and should have equal human rights as every citizen.

Dr Cousens warned that there is no actual liberation on the left-hand path. People who use drugs can become possessed or often have entities, according to Dr Gabriel Cousens.

Insanity in the mental body is the heavy fate which those must endure who have followed the path of selfish cruelty through many incarnations, using intelligence as a means to serve selfish ends and using it deliberately, knowing that they were doing wrong. Insanity in this form is a means by which the Ego sometimes stops the progress of man on the left-hand path. In this way it is a blessing in disguise.

Sometimes totally innocent people have fits of insanity when the pain is too great to handle. It's nature's way to escape a burden that no normal person can handle. As Arthur Schopenhauer said wisely: "The genius suffers the most".

Sri Aurodindo gives as advice in Light on Yoga.

"Those who fall into madness have lost the true touch and have come into wrong contact. This is due either to some impurity and unspiritual desire with which the seeker begins the path, or to some insincerity, egoism and wrong attitude, or to some weakness in the brain or nervous system which cannot tolerate the Power that it has called down.

The safest way is to follow the guidance of one who has himself attained mastery in the path. But this guidance must be followed unconditionally and sincerely; you must not allow your own mental being and its ideas and whims to interfere. It goes without saying that it must be a true guidance, not the guidance of a beginner or an impostor."

The aspirant has 3 things to do:

1. Purify, discipline and transmute his threefold lower nature.
2. Develop knowledge of himself, and equip his mental body,build the causal body (soul) by good deeds and thoughts.
   
3. Serve his race in utter self-abnegation.

More info : 

Kundalini, Evolution and Enlightenment by John White.