Trust is the cornerstone of any successful relationship, according to psychotherapist Dr. Bill Cloke in “5 Ways to Rebuild Trust After It’s Broken" on the Care2 website. You can break your girlfriend’s trust in various ways, such as lying, anger, addictions, infidelity, flirting, abuse or violating her confidence. If you've lost your girlfriend's trust, you'll have to work hard to regain it, if she is willing to forgive you.

Confessing Your Actions

Confess how you violated her trust and accept responsibility for the destruction of her sense of safety, security, respect, love and friendship. She will want to know why you violated her trust. Answer her questions to the best of your knowledge. Do not lie or blame her or anyone else for what you did. Take full responsibility for your actions. Describe not only your actions, but also the consequences of your actions on others, such as shame, loss of employment or financial loss. However, if there are details that will cause her more pain, you might omit them, suggests Cloke.

Her Response and Making Amends

Give your girlfriend a chance to explain how you hurt her. You need to listen to her describe the damage in detail. Retell her story in your own words so she knows that you have heard her. Apologize to your girlfriend now that you fully understand what you've done. Ask her how you can make amends and then be willing to give her what she needs to repair the damage, suggests marriage and family therapist Sheri Meyers in “For the Betrayer: 8 Things You Must Know and Do to Rebuild Trust After an Affair” on the Huffington Post website.

Demonstrate True Remorse

It will take time and patience to prove that you have changed. Be the best and most trustworthy boyfriend you can be. Don't deceive your girlfriend again, such as telling her that you have to study when you want to spend time with friends. If you have anger, addiction or abuse issues, get professional help to overcome them. Only make promises you can keep, suggests Meyers. Do what you say you're going to do and be where you say you will be when you say you will be there.

Respect Her Decision

Your girlfriend has the final say about whether she will forgive and trust you, affirms developmental psychologist Susan Krauss Whitbourne, Ph.D., in the article "Overcoming Betrayal: It’s a 2-Way Street" on the Psychology Today website. She might say that she cannot bring herself to trust you again, that the hurt is too much. Respect her choice and allow her to walk away if she desires. Learn from your mistakes and don’t violate the trust of your next girlfriend.