Too much sleep

If we decided to sleep more, as some retired people do, we would sleep too much. Of course, that is no objection to sleeping a lot. Since intellectual work takes a lot out of our physical organization, people doing that kind of work need much sleep. But if we sleep too much, we have too many new life forces and these then begin to proliferate; the human being then abounds with life forces. This surplus of life forces leads to illness. 

Source: Rudolf Steiner – GA 154 –  Presence of the dead: LECTURE SIX: FAITH AND KNOWLEDGE – Prague, April 17, 1914