Apologizing can be hard for some people to do, so if someone is taking the risk of stepping forward and being the one to apologize first, hear them out. If you feel like the apology is valid, give your side of why you got mad in the first place and give your own apology to settle things once and for all. But if you are not ready to accept the apology, let the person know calmly so that you do not end up fighting again and stepping further away from apologizing to each other.