Extract from letter Nine of Rilke’s “Letters to a Young Poet”:
And about emotions: all emotions are pure which gather you and lift you up; that emotion is impure which seizes only one side of your being and so distorts you. Everything that you can think in the face of your childhood is right. Everything that makes more of you than you have heretofore been in your best hours is right. Every heightening is good if it is in your whole blood, if it is not intoxication, not turbidity, but joy which one can see clear to the bottom. Do you understand what I mean?
And your doubt may become a good quality if you train it. It must become knowing, it must become critical. Ask it, whenever it wants to spoil something for you, why something is ugly; demand proofs from it, test it, and you will find it perplexed and embarrassed perhaps, or perhaps rebellious. But don’t give in, insist on arguments and act this way, watchful and consistent, every single time, and the day will arrive when from a destroyer it will become one of your best workers—perhaps the cleverest of all that are building at your life.
Know Thyself 