"Others live on in a careless and lukewarm state - not appearing to fill Longfellow's measure: 'Into each life, some rain must fall.'"

In this quote, Mary Todd Lincoln is assessing the various ways in which individuals live their lives. She recommends that some individuals live in a negligent and lukewarm manner, not fully welcoming the opportunities and experiences that life has to offer. These people do not appear to live up to the standard set by the poet Henry Wadsworth Longfellow, who thought that every person's life ought to be filled with significant minutes and obstacles. Mary Todd Lincoln then referrals Longfellow's popular quote, "Into each life, some rain should fall", which advises us that life is not constantly easy which we need to deal with troubles and challenges. Overall, this quote works as a pointer to live life to the max and welcome both the excellent and the bad.