If there is no Acharei- After in our Yom Kippur, there will be no guidance and direction. It will just continue to be a spiritual high and fad that will slowly fade away. 2 themes of Acharei -Mos; After the Death; 1) Sanctaty of Yom Kippur-Holiest day of the year.   2) Intimate profanity- Lowest of the low. Various opinions about how the Kohen Gadol counted as he sprinkled the blood in the Beit Hamikdash.