Admitting you have done something wrong and saying sorry can be difficult, especially when you want to prove your remorse to your girlfriend. If you want to move on in your relationship however, learn when to say sorry and how best to do it. Your girlfriend will appreciate your honesty, sincerity and effort through behaviour instead of just words.
Make a Gesture
If you made a mistake and upset your girlfriend, show her that you didn't mean to hurt her and you are sorry. Actions speak louder than words. For example, if you forgot your anniversary, planning a special day for just the two of you. Or if you didn't help her with something, offer to help her out with something else instead that you know will lighten her load. Find a way to do something kind and thoughtful to make up for your mistake.
Say it with Words
Sometimes an apology that comes straight from the heart is the most effective. However, just saying "I'm sorry" may not suffice; tell her you know where you went wrong and why it upset her, so she knows you mean it. Don't include excuses in your apology because it will seem less sincere. You may want to write a letter to send collect your thoughts and compose a heartfelt apology that will convince her of your remorse.
Make a Change
Show your girlfriend you are sorry by changing whatever it is about yourself that caused her to be upset. This means making an effort to make sure that it never happens again. For example, if your girlfriend was upset because you drink too much when you go to a bar and end up embarrassing her, then cut down on your drinking. If she caught you flirting with another woman, apologise by cutting off any with the woman to remove any temptation to do it again. Let her see that you can be trusted.
Give a Gift
Depending on what you did wrong and how your girlfriend is feeling, you might want to give a gift. Make sure it is personal so she can see you have given it thought. Give her flowers with a heartfelt note attached or make her a CD compilation of all of her favourite songs. The right gift can demonstrate that you care for your girlfriend and that you want to make things right.