You can't blame yourself for that. Sometimes change isn't always good, but it isnt always bad too. But it always happens. Accept it and move on. If you ever cross paths again embrace it and try to have better vision on things this time around.
It depends on how you feel. Even though you feel strongly for someone, it is not worth it to keep hanging on when they make your life miserable. You should be with someone who makes you happy so in my opinion you weren't wrong.