But Goethe tells us in his greatest poem that Faust lost the liberty of
his soul when he said to the passing moment: "Stay, thou art so fair."
And our liberty, too, is endangered if we pause for the passing moment,
if we rest on our achievements, if we resist the pace of progress. For
time and the world do not stand still. Change is the law of life. And
those who look only to the past or the present are certain to miss the
future.
John F. Kennedy
"Address in the Assembly Hall at the Paulskirche in
Frankfurt (266)," June 25, 1963, Public Papers of the Presidents: John F. Kennedy, 1963.
Source: The Kennedy Library online.