The person who broke you cannot be the one to fix you. Remember that. Sometimes in a moment of weakness we want to fall back to what is familiar. It's so easy to do it, but don't. You may be sitting in your room at night, alone, wondering where it all went wrong. You may be missing them, but don't succumb to the loneliness.
No matter how much they claim they change, don't go back. People will tell you what you want to hear. Even if you decided to give them another chance, things won't ever be the same. The beginning of the relationship was really good, and you may never have that again. If you take them back, they may hide who they really are to trap you in. They may act like they have changed, and they may do or say anything for you to believe them. Hard times bring out the worst in people, and you will realize one day, they in fact never changed. You still love them, but you need to realize, you don't love them, you love the idea of them. You are not weak for wanting to go back and thinking they have changed.
Your past is your past for a reason. If you want a new and better life, you cannot go looking for it in your past. Moving backwards will only increase the time it takes you to move forward. You can't continue to go backwards and be with people who are meant to be in your past, if you want to move forward. You had a good reason to let go of the person. Some people just aren't meant to be together, and that's okay.
You are worth so much more. You are worth more than being with someone who hurts you time after time. You are worth more than someone who drags you down constantly. You deserve to be with someone who brings out the best in you. You deserve to be in a happy, healthy relationship. You deserve the very best, and nothing less.
It's going to be hard to deal with the pain and loneliness. It's going to be hard to not pull out your phone and fall right back into their trap. The pain and loneliness will heal, and you will be okay.