The spiritual scientist needs to stand with both feet on the ground 

What I have described here is the force of higher knowledge, which in some sense only occurs when the spiritual scientist gives himself over to such higher insights. It is not something that takes hold of him or makes him into a mystical dreamer, living outside of life. It is something he can handle, something that he can consciously summon up, in the same way, that one performs a scientific experiment and returns to ordinary life afterwards; in which one is a balanced, thoughtful person with all the soberness needed in life. Indeed, one who tends to have a pathological state of mind in ordinary life, who cannot use his full personality in ordinary life like any other person, can also not in the real sense of the word be a spiritual scientist.

Source (German): Rudolf Steiner – GA 77a – Die Aufgabe der Anthroposophie gegenüber Wissenschaft und Leben – Darmstadt, July 29, 1921 (page 145-146)

Translated by Nesta Carsten-Krüger