Getting back the trust of someone you love is an admirable but delicate task. Once you have broken someone's trust, his feelings toward you will be a mix of bitterness, confusion and resentment. If he was extremely close to you, he will be questioning the fact that he trusted you in the first place. However, if you made a mistake, recognize it and are genuinely sorry, there are a few important steps you can take to win back someone's trust.
Apologize for what you did to hurt the person you love. Doing so is the most fundamental, basic thing you can do to earn her trust back. Try to put yourself in her place to imagine the pain she is going through. When you apologize to her, have patience. Do not play any games, demand that she accept it right away, or expect any sort of immediate positive reaction. Although you are putting yourself out there and making yourself vulnerable to her criticism, it is your duty to let her know how you really feel without being manipulative. A simple, sincere apology will go a long way.
Express your desire to be close to him again. After you have apologized to him, tell him exactly how you feel, whether it be through a letter, a long conversation, or anything that will show him what you are experiencing and what you want out of the relationship in the future. This is separate from apologizing; an apology is simply your acknowledgment of your failure and your requesting forgiveness. However, when you express yourself and let the person know exactly how you are feeling now, you give him a little understanding of what you are going through and how you feel about the relationship.
Give her space and time to think and gain trust back for you. This is hugely important in the process of rebuilding your relationship. While she likely wants to believe everything you are telling her, a huge part of her that has been injured protests against letting you into her heart again. Letting her have space and patiently waiting for her to trust you demonstrates that you acknowledge that what you did was painful, and understand her need to take time for herself.
Listen to him when he is ready to talk. When you have apologized, expressed yourself and given him time to think, be ready to listen to him when he wants to tell you exactly how you made him feel. Be prepared; he likely has feelings of deep anger, resentment and sadness built up in his heart. While you may be devastated when he lets it all out for you to see, this is a vital step in the recovery process of relationships. Your loved one needs you to understand the extent of the damage that was done in his heart and you need to understand it and learn the significance of your actions in his life. Pay attention to every word the one you love has to say, and understand that rebuilding a relationship will take time, effort and patience on your part.