Question about a passage from VoS

“A rational man knows that one does not live by means of “luck,” “breaks” or favors, that there is no such thing as an “only chance” or a single opportunity, and that this is guaranteed precisely by the existence of competition. He does not regard any concrete, specific goal or value as irreplaceable.”

How does competition guarantee that there will be more than one opportunity to achieve a particular value, and if one holds a particular job as being more desirable than all others, why wouldn’t he consider it irreplaceable?

Citations are customary please, for context at least: book, edition, essay, page, paragraph

Citations are customary please, for context at least: book, edition, essay, page, paragraph

 

The Virtue of Selfishness, The “Conflicts” of Men’s Interests," page 63 (different versions may have different page numbers).