“A man must preserve himself for his work and must be thoroughly acquainted with the road to it. A man, dear, is like the pilot on a ship. In youth, as at high tide, go straight! A way is open to you everywhere. But you must know when it is time to steer. The waters recede – here you see a sandbank, there, a rock; it is necessary to know all this and to slip off in time, in order to reach the harbour safe and sound.”