There is no doubt that being on the receiving end of deceit, betrayal, or any form of dishonesty is painful. When it is in your most significant relationships, that is devastating. Once it has happened, there's nothing a good friend, parent, or confidante can say that will make you feel better. Uplifting phrases and "at leasts" will only dig you deeper into the rut than you already are. Once the damage is done, the relationship will be forever changed. But, here you are... you have somehow survived the shipwreck. Your life is not over, and there is hope. So, how do you begin to rebuild after what feels like a level-five emotional catastrophe?
Trust yourself.
Experiencing betrayal can lead you to completely question your thoughts, actions, and intuitions. Don't. If anything, reflect back and identify the times when you had a "hunch" or "intuition" but perhaps ignored it due to denial or just wanting to believe the best in someone. There's nothing wrong with wanting to see the best in people... in fact, that says so much about who you are as a person willing to take the risk of trusting.
Continue to request honesty in your future relationships. Just because you have experienced a partner's inability to be honest with you does not mean that is what you deserve, caused, or what you are destined for. Be aware of how you are feeling. Listen to your thoughts. Keep your values and believe in your internal compass. When you can re-cultivate self-trust, you will be able to trust others again. But trusting others has to start with you trusting you.
Your new best friend is Time.
Because, yes, time does heal. It does not fix, but it is a part of your solution. Move slowly and focus on rebuilding that self-trust. Understand that healing will come over time (with work) and that this can be a comforting thought. People go to the gym consistently for one week and get upset that they don't see results and only feel sore. It doesn't work that way! Emotional healing is a different kind of fitness that requires daily commitment. Yes, you are entitled to a few cheat days and moments of emotional burnout, but get back on track ASAP. You are worth it.
Create new situations in your life.
Get a new hobby. Revisit an old hobby. Spend time with that high school or college friend that you have been meaning to catch up with. Create new environments around you so that you get a little variety. Look up free outdoor activities near your area, or find something just for you to re-connect with yourself (yoga, running, crafting, praying/meditating, cooking). The hardest part about this one is starting. Once you get there, the doing comes easy. So, start. See what difference you notice in yourself emotionally and energy-wise.
Learn.
Were you cheated on? Did someone disclose a huge secret that destabilized the whole family? Was substance abuse involved in your particular situation? It can be empowering and liberating to do research on the reasons why people act out the way they do. I recommend seeing a professional like a therapist, psychologist, or someone credible who understands how we develop and function. Chances are, there is a lot of pain behind the person who hurt you, too. As the AA saying goes, "hurt people hurt people." Pain is often masked by anger, control, cheating, drug using, and more. Don't make the choice of believing it was because of you alone. Let yourself learn and grow from what has happened.
Entertain the idea of forgiveness.
This one may happen a little further down the road, but that's right -- I said it. There are many misunderstandings about forgiveness, so I will cut to the chase and tell you the secret: Forgiveness is for YOU. Yes, we may accept apologies from others, but this is not the same as saying we forgive them. True forgiveness is letting go and releasing the hold of negativity that the event or person has over you. It is also recognizing that you have allowed that hold around yourself, and, at any moment can request that it be removed. Just say the word.
This step will be much easier once you have done the "learning" to understand the other person's behavior a little more. Forgiveness allows more room inside of you for empathy, love, and compassion. And from that foundation, you will begin to rebuild.