Handling bad thoughts and influences

All these thoughts and influences come really from outside, from universal Nature—they create formations in us or get habitual responses from the individual being. When they are rejected, they go back into the external universal Nature and if one becomes conscious, one can feel them coming from outside and trying to get a lodging inside again or reawaken the habitual response. One has to reject them persistently till no possibility of response remains any longer. This is hastened much if a certain inner calm, purity and silence can be established from which these things fall away without being able to touch it.

Ref : Letters on Yoga Vol. IV