If during the day an ill feeling comes to a person, towards a friend or relative a feeling of hatred, a feeling of annoyance, a feeling of criticism, a feeling of bitterness, and he wishes to protect his heart from such an impression, he should not think about it, he should not let it enter, knowing it to be poison. It is just like taking a poison into one's blood, introducing a disease. Any bad impression coming from outside and kept in one's heart produces disease. The bitterness that one takes from others who perhaps have done something one did not like, or to whom one feels bitter, is kept in one's heart, and this is just like injecting poison into one's heart. That poison develops there till it breaks out as a disease in one's physical being.