The title caught my eye so I needed to pop in and read. I also have a poem with the same title and I invite you to stop by and check it out. Regret is so individual, based on life circumstances and mistakes that can last for eternity. A constant reminder of what could have been or what never was. In your circumstance, a person lost. My only recommendation is to add more insight into the circumstances that brought about the regret itself. It may help the reader relate to the feeling rather than just a "love lost" identity.