I agree with the suggestion of Richard and Linda Thompson's "Shoot Out the Lights", but also take a listen to the post-split, follow-up release by just Richard - "Hand of Kindness." Tracks like "Tear Stained Letter", "A Poisoned Heart and a Twisted Memory", and "How I Wanted To", among others put it all right out there. (Richard Thompson has written plenty of sad relationship songs over the years, but his music has gotten me through plenty of ups and downs over the years.) If you're unfamiliar with him, start exploring!!