The third danger against which the aspirant must guard himself is becoming obsessed by his own embodied ideas, be they temporarily right or basically wrong. Forget not that all right ideas are temporary in nature and must eventually take their place as partial rights and give place to the greater truth. The fact of the day is seen later as part of a greater fact. A man can have grasped some of the lesser principles of the Ageless Wisdom so clearly and be so convinced of their correctness that the bigger whole is forgotten and he builds a thought-form about the partial truth which he has seen which can prove a limitation and keep him a prisoner and hold him back from progress... he forgets his own brain limitations and that the truth has come to him via his own soul and is consequently coloured by his ray, being subsequently built into form by his personal separative mind. He lives but for that little truth; he can see no other; he forces his thought-form on other people; he becomes the obsessed fanatic and so mentally unbalanced, even if the world regards him as sane.
(Treatise on White Magic pp. 489-90)