We are like sailors who have to rebuild their ship on the open sea, without ever being able to dismount it in dry-dock and reconstruct it from the best components.
-- Otto Neurath (Wikipedia has a slightly longer version)
Found that quote in this article that starts off with an implausible story about the Titanic, and keeps you hooked all the way to the end.
I also found this Joseph Conrad quote that appeals to the materials engineer in me:
But all this has its moral. ... Yes, material may fail, and men, too, may fail sometimes; but more often men, when they are given the chance, will prove themselves truer than steel, that wonderful thin steel from-which the sides and the bulkheads of our modern sea-leviathans are made.
-- Joseph Conrad, Some Reflections on the Loss of the Titanic (1912).