Bism Illah wa as salaamu alaykum wa Rahmat Allah wa Barakatuh.
A reader asked for my take on how to you rebuild trust after repeated betrayals, so here it is - my own personal view.
When you have someone in your life that hurts you, commits indiscretions, or outright sins, and you come to a stage where you cannot trust them, don't. Not trusting someone doesn't mean you cannot live with them, enjoy time with them, love them. It simply means that you know certain of their weaknesses and cannot rely on them to overcome them. It does not mean that you don't encourage them or support them to overcome those weaknesses though. It doesn't mean that you give up hope and dua' for them, either.
There is a saying, expect nothing then everything will either meet or exceed your expectations. With our loved ones we don't want to think badly of them or expect them to do wrong, but getting over their betrayal lies in accepting their humanity and failings. Pray to Allah to keep bad feeling from your heart and replace it with understanding, mercy, and forgiveness. If you want or need to feel some kind of trust in that person, consider areas that they have always been consistent in and focus on them. However, there is no point setting yourself up for continuous disappointment or hurt by trusting them in the things they cannot be trusted with, when they haven't conquered their qareen/shayateen/nafs.
An example I can give is in raising children. You may have a child who tells lies. You may remind the child that this is wrong and even negatively reinforce the behavior (in other words punish them). You hope that the child learns and doesn't lie again. However, knowing the child's character, will you be surprised if the child lies again? Disappointed, probably but surprised, no. You know that lying is the child's weakness. There is, in my estimation, little or no difference with a spouse, parent, or friend. If one day you find that five years have passed and the child hasn't lied, perhaps you will find that over that time your trust in them has grown. It isn't something that needs work, it is something that happens naturally when there are no repeat offenses or they become very few and far between.
This is the direct opposite of what we are supposed to do with Allah, from Whom we expect the best because He is Perfection. My view is very simple: trust only Allah completely, not mere humans.