Summarize:

Lying will only further erode trust and create more stress for you. If you are dishonest, you will continue to worry about being caught. Be honest and forthright to prevent potential future betrayal and delay the process of regaining trust. Being forthcoming will also allow you to explain your behavior in the best possible way. Your partner may assume the worst and others may exaggerate what happened, so take control of your story. Your partner will likely be upset, and may use negative language. Even if you know you did something wrong, this may cause you to become defensive of deflect blame. It is important to remember your partner is in great pain, and they need to express that.  When you start to feel the urge to defend yourself, imagine how you would feel if your partner betrayed your trust. This will help you to recognize your partner's communication as an expression of pain, rather than an attack.  Nothing you do will ever justify abuse. If your partner becomes physically aggressive, verbally abusive, or threatens you in any way, you should leave the situation immediately and seek help. to your partner. Show your partner you care about their thoughts and feelings by restating and reflecting what they communicate to you. Restate their communication by paraphrasing. Then, reflect by stating the emotion they are expressing. For example, if your partner says "You said you'd be there, but you weren't. You knew how important this was to me!" then you could say "I realize I wasn't there for you, and that I disappointed you." . It is very important your partner feel heard and understood. Your betrayal represents a disregard for your partner's well being. Demonstrate you care by describing how your behavior likely affected your partner. For example, "My behavior was hurtful and violated your trust."  Try to avoid using the phrase "I know," when talking about others' feelings. While not meant to offend, some people may interpret it as patronizing.
Take responsibility for your behavior, and admit what you did. Put yourself in their shoes to avoid becoming defensive. Listen actively Validate their feelings