Which of the following is the best definition of the term "bookend"

"if we never experience the chill of a dark winter, it is very unlikely that we will ever cherish the warmth of a bright summer’s day. nothing stimulates our appetite for the simple joys of life more than the starvation caused by sadness or desperation. in order to complete our amazing life journey successfully, it is vital that we turn each and every dark tear into a pearl of wisdom, and find the blessing in every curse." anthon st. maarten, divine living: the essential guide to your true destiny. what does this quote mean to you? this isn't for anything in particular, i just wanted to know. : )