And as to feelings: all feelings are pure that focus you and raise you up. An impure feeling is one that only comprises one side of your nature and so distorts you. Any thoughts that match up to your childhood are good. Everything that makes more of you than you have hitherto been in your best moments is right. Every heightening is good if it occurs in the quick of your bloodstream, if it is not an intoxication, not a troubling but a joy one can see right to the bottom of. Do you understand what I mean?

And your doubts can become a good quality if you school them. They must grow to be knowledgeable, they must learn to be critical. As soon as they begin to spoil something for you ask them why a thing is ugly, demand hard evidence, test them, and you will perhaps find them at a loss and short of an answer, or perhaps mutinous. But do not give in, request arguments, and act with this kind of attentiveness and consistency every single time, and the day will come when instead of being demolishers they will be among your best workers – perhaps the canniest of all those at work on the building of your life. (Letters to a Young Poet)