The feeling of regret is the most painful feeling that I have ever experienced. It sticks, lingers and dominates. You wish that you could forget about it but you can't. You listen podcasts about letting go, and hope that one day you can be enlightened. So that you can finally forget about the things that torture you, and let go of your attachments. This is beautiful. When you use "Couldn't" It gives the impression that you already tried and stopped trying. I think that you are trying to talk about a constant struggle, that is why one of your sentences is "It keeps coming back". That is why I changed "couldn't" to "can't". That is also why I changed the past tenses to present tenses, because it is something that happens often. I hope this helped!

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