Leftover feeling in Inner demons

Just to clarify, I don’t want to go back to the relationship I was in, I have moved on and I am definitely happier but there is something that I just can’t seem to shake. Maybe it’s because he cheated on me, I don’t know. Do you ever get closure on a situation that you aren’t sure why it happened? Is that why I feel like I wasn’t good enough even though I’m the one who left? The relationship I was in, was ruined by drinking, unfaithfulness, disrespect and lies. And that’s something I would never go back to, I just want to know why, why do I still feel like I wasn’t good enough? Will it ever go away?