The Arizal states that Yom Kippur is Yom Kippurim, a day like Purim. 

The Shelah explains that just as the essence of Purim is fraternal love and kinship expressed in and engendered by mishaloch manos (sending presents to one’s friends) and matanos lievyonim (gifts for the needy), so too on Yom Kippur one is without jealousy, enmity or ill will towards one’s fellow man, similar to an angel.  

It is for this reason that Yom Kippur is a day when our sins are forgiven.

~ R’ Chaim Shmulevitz zt”l