How we cite our quotes: (Page.Paragraph)
Quote #1
Sigmund Freud stresses in his writings the passages and difficulties of the first half of the human cycle of life—those of our infancy and adolescence, when our sun is mounting toward its zenith. C. G. Jung, on the other hand, has emphasized the crises of the second portion —when, in order to advance, the shining sphere must submit to descend and disappear, at last, into the night-womb of the grave. The normal symbols of our desires and fears become converted, in this afternoon of the biography, into their opposites; for it is then no longer life but death that is the challenge. (10.2)
Again, look at the way Campbell phrases it here. Death is a "challenge," and part of this larger cycle. You have to accept and embrace it for the cycle to continue revolving the way it's supposed to.
Quote #2
Only birth can conquer death—the birth, not of the old thing again, but of something new. (15.2)
The cycle; it all comes back to the cycle. We do not stay static and unchanging, for that really is death. We need to change, just as the universe changes, and that usually means surrendering the old – in other words dying – in order to bring forth something new.
Quote #3
The idea that the passage of the magical threshold is a transit into a sphere of rebirth is symbolized in the worldwide womb image of the belly of the whale. The hero, instead of conquering or conciliating the power of the threshold, is swallowed into the unknown, and would appear to have died. (83.1)
Rebirth and immortality can't happen until you die. In this case, Campbell is talking about surrendering your fears and embracing the scary stuff in front of you. You may die but then discover whatever it is you're looking for and be reborn.