He or she was mortal after all like everyone and everything.
And although he or she is gone, that person had a lot of good days, moments of being, pleasure, connectedness, laughs, and triumphs. In that, perspective on all his/her and all our mortalities. It is and was their presence, innocence, basic goodness, humor, character, talents, and imagination that will and would be missed.
“Any man’s death diminishes me, because I am involved in Mankind; And therefore never send to know for whom the bell tolls; it tolls for thee.” –John Donne, Devotions, XVII