What is going on with your sudden attacks of fatigue? (I remember with horror how inconsiderate I often was about that. Terrible! But I know you don’t hold that against me); and shouldn’t you have Papa give you a few Pervitin for when you are on guard at night? Here it is often used for this purpose, and I recently tried it out myself. It is very good. God ahead and talk it over.
Dietrich Bonhoeffer, letter from Tegel Prison to Eberhard Bethge, November 18, 1943 (DBW-RE, p. 167)