How do people stay in a relationship with a person who has emotionally hurt them so badly but continue to want to be with them?

I have been noticing lately that people will cheat on their significant other and the person that was cheated on still wants to stay with this person. I was in the same situation and as much as I had loved my ex I couldnt stay in the relationship (even though i wanted to bc i loved him) because the trust was gone. I struggled every single day trying to gain the trust back but I was full of anxiety everyday wondering if he will do it again. I notice that people I know feel differently about the situation and I wish I were able to do that. They are able to move on and continue the relationship and I wish I were able to do that but I cant. I also have been noticing this in other areas in relationships and not just with cheating. I have a friend who is divorced and the ex husband took her children away from her for almost a year. They were constantly in disagreement when they were married and the husband was doing things after the divorce that were wrong. My friend wasnt perfect either; however, the husband reached out to her so let her see her son. This is great and I am so happy for her but she is thinking about getting back with her husband! They got divorced for a reason and I think that she is so quickly to forgive. I think that it is good to forgive but it doesnt mean get remarried. What are your thoughts about people who give other people another chance when they have hurt their relationship so badly? When do you draw the line and stay broken up? Are you able to continue a relationsip with someone you love even though they had cheated on you? What are your thoughts?