Faith or Enthusiasm?

I tell you, if you haven't read any Dietrich Bonhoeffer, you really oughtta.
A quote:

Dear brethern. our real trouble is not doubt about the way upon which we have set out, but our failure to be patient, to keep quiet . . . And we simply cannot be constant with the fact that God's cause is not always the "successful" one, that we really could be "unsuccessful" and yet be on the right road. But this is where we find out whether we have begun in faith or in a burst of enthusiasm.

(Hat tip: Live Free or Die)