I agree with the others. Its about validating someones feelings for something you did that hurt them. Forgiveness is on their part so making excuses doesnt help at all. I find it can be your tone of voice too. And maybe a hug afterwards if they'll let you. And if you cant look them in the eye the whole time, because sometimes things are so shameful and you want to look down, but at some point you should make eye contact. But like rcat said, if you're apologising more than once for something they wont believe you anymore.