When doubt arises
Doubt takes many forms. One is fear that you'll hurt yourself by going forward. Another form of doubt is feeling that you've misunderstood your life and that you're constantly making a fundamental mistake. Being without doubt has nothing to do with accepting the validity of a philosophy or concept. Absence of doubt comes from trusting in the heart, trusting yourself. Being without doubt means that you connect with yourself, that you experience mind and body being synchronized together. When mind and body are synchronized, then you have no doubt.
Chogyam Trungpa, from 'The Sacred Path of the Warrior'