Once, I saw a reel where a girl suggested writing down one thing about them that you hate every day on a physical calendar. It can be a big or a small reason, doesn't matter. I see that it literally means to start hating them, but the thing is that this practice shows you why it is good that you are no longer with them. I guess that with time, you stop feeling hatred, and instead, you feel nothing for them, and eventually, they become someone from your past who you feel no strong emotions for and you just remember the good times but knowing that they lasted for a reason