Inquiring doubt uses mindfulness for investigation. Mindfulness practice helps overcome doubt because it acts with the confidence that it is possible “to know,” or be mindful of how things are in any given moment. Or if you encounter a situation where all you know is confusion, then with mindfulness at least you have the clarity to know that you do not know. This distinction between knowing and knowing you do not know is surprisingly grounding and can stop doubt from working its way into your nervous system.
This insight leads to the first step in working with doubt: cultivating “don’t know mind,” which dispels the myth that you are always supposed to know, never to be in doubt. Likewise, you can examine your mind to see if you have an expectation that you should be perfect, which prevents you from realizing that painful mistakes are part of living life. New knowledge creates new uncertainties, so that which is causing you doubt can be appreciated because it signifies new possibilities to learn about yourself.
by Phillip Moffitt, http://dharmawisdom.org/teachings/articles/lost-doubt