The best way to awaken our clairvoyant forces is to ensure that as much effort is spent on the development of our morality as it is on achieving clairvoyance. It cannot be emphasised enough that building up a moral character is key to the proper unfolding of clairvoyant faculties.
[…] We can observe that people who develop clairvoyant faculties but neglect to refine their moral attributes will display bad habits of character they never, or hardly ever, possessed. Many, for instance, will become great liars, as they start developing their clairvoyance.
It is particularly dangerous for the character of a human being when the faculty of spiritual hearing unfolds: clairvoyance is less dangerous than what we might call clairaudience, or spiritual hearing.
Source (German): Rudolf Steiner – GA 143 – Erfahrungen des Übersinnlichen/Die drei Wege der Seele zu Christus – Zürich, 15 January 1912 (page 49)