The mind is a malleable thing, sensitive to outside influences. Waitzkin, in The Art of Learning, talks about how a Soviet player unknowingly interrupted his natural rhythm of thought by tapping a chess piece against the table. The sound was barely audible, yet it caused him to make careless errors at critical moments.
Only when the tactic was explained to him was he able to notice it and counteract it.
Our minds are not immune to outside influences, especially if they are subtle and we aren’t paying much attention. Just what are we putting into our mind? Are we being intentional about it? Are we paying careful attention to what we read and watch and allow to enter our ears? Even a whisper has the potential to alter our behavior.
To be careless in this seems dangerous. In this, we should train to be as wise as serpents (Matthew 10:16).