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. Change is the law of life. And those who look only to the past or present are certain to miss the future.
John F. Kennedy (1917-1963) US President (1961-63)
Speech, Paulskirche, Frankfurt, Germany (25 Jun 1963)
(Source)
Variant in some locations: "... And those who look only to the past are certain to miss the future."