A warning to those who want to get even.

Remember that harbouring thoughts of anger―hatred―revenge―or any form of getting even with someone whom you feel has wronged you―open your aura to those in the astral world who harbour similar thoughts―who will strive to enter your consciousness over the avenue thus opened and stir up and augment your hatred and urge you to execute a far more terrible form of getting even than you would entertain or even think of by yourself. 

The practice of forgiving others is, therefore, enjoined on all occult and spiritual students, for as long as you hold antagonism toward anyone you bind yourself to that one with a powerful tie, and also open yourself to obsessing forces along that line.

Realms of the Living Dead—A Brief Description of Life After Death