Mistakes are natural, we are humans and we're not perfect. There are times we do things that hurt others, intentional or unintentional.
Some of us will make it up to the people they caused pain, specially if we never meant to hurt others. Accepting one's fault and asking forgiveness are some of the things that we'll do. But why do some people find it hard to say sorry? Instead of apologizing, they find excuses to what they did and defend themselves, or worse, deny their fault. Okay then, if it's hard to say sorry, the important thing to do instead is never to repeat the same mistake. That can be another way of showing sincerity, and more effective in making up with the people we hurt rather than saying sorry easily but still committing the same mistakes over and over again.