Everyone is different, and what I'm about to share with you might not work for everyone, but if it works for a few it will be worth it. My take is that you shouldn't even attempt to stop caring, because it's simply against your nature. It isn't going to work and it might even make you feel worse inside. You should also realize that your immense capacity to love someone even after they've hurt you is something you should embrace. I know it sounds unorthodox, but bear with me.
Something we try to do as humans is avoid cognitive dissonance. We want things to be black and white so that we can easily understand the world. However, some of us aren't able to see the world in black and white. We know that the varying grays exist, and we can't unsee that.
Forgive yourself for not being able to forget what you liked about a person, while you also make a conscious effort to remember why things ended. You are allowed to both hate and love a person at the same time. You are allowed to have days that you reminisce and want them back tremendously. You are also allowed to have days that you are glad they are no longer in your life. Accept that these two dimensions of hating and loving a person can exist within you simultaneously.
Maybe you can resonate with the feeling of frustration that comes when you can't stop caring about people you know couldn't care less about you. I think if I had a dollar for every time that happened I'd be rich. What I realized over time is that caring more about others is nothing but a reflection of how boundless the love in my heart is. I don't believe in the "caring less" competition. To be honest, it's a ridiculous notion that caring less about someone somehow makes you the winner of life. It has nothing to do with the quality of you as a person that they don't care about you anymore. We can also care about people while acknowledging that they really aren't that great... we're just the type of people who happen to make deep connections regardless.
Caring more about someone has no impact on the value of a person. Let yourself care, and know that it can happen even when you've let them go. It isn't an indicator that you haven't progressed or moved on. Just because you still care doesn't mean you ever have to talk to them again. It certainly doesn't mean you should go back to them and try to make them care back. They won't, and that's their loss. Also, their lack of care towards you may help you move on, but it still doesn't change that fact they are them and you are you. They are built colder than you are, and you shouldn't try to be like them. You are perfect the way you are, even if you care too much for other people to understand. I feel a little bad for the people whose hearts are not as capable of love and caring as mine is. They are just so oblivious to all of the vibrancy they are missing out on. Imagine how dull and unimportant life would be if you were that devoid of emotion.
One day they will be a distant memory, but sometimes the heart just doesn't forget no matter how much you try. The bottom line is that you should accept and forgive yourself for all of the feelings you have within you that come and go. Although those old memories will remain everlasting in your heart, you will recognize that you still have plenty of room for vibrant, new, and beautiful memories to form. Preferably with people who don't make you feel like having a big heart is something you have to feel afraid of showing.
