The Rambam teaches us, “Yom kippur wipes clean wrongs committed between a person and God. For Yom Kippur to atone for sins between people a person must go and ask for forgiveness.
The Rambam continues, “It is forbidden for a person to be cruel and refuse to be appeased. Rather, he should be easily pacified, but hard to anger. When the person who wronged him asks for forgiveness, he should forgive him.