There's a story told on page 24 of Ursula Tamussino's book. September 1965 in Vienna, Lucia Popp "cracked" in one of the Queen of the Night arias and got depressed. Lucia was in such state of despair and on the point of giving up singing and going back to Bratislava, but was talked out of it by Fritz Wunderlich.
Imagine what favor that nature's wonder, Fritz Wunderlich, granted to the world, by saving Lucia Popp for her art. Listen to her, the very last recording of LUCIA POPP, "Non Più Di Fiori" and try to imagine opera's history without her. No way! Thank you Fritz!!