HEA means Happily Ever After which, in a book labeled a romance, is necessary. Because readers will expect it, and if you don't deliver they won't read your "romances" again. So, as always, know what your genre requirements are and meet them. Readers' Rules are Readers' Expectations that you break at the peril of your career.
I think I told you that I had a friend who was judging a romance contest and got an unpublished work where the heroine killed herself in the end. NOT a romance, and the writer didn't know it.
READ in your genre, KNOW your genre, MEET the set-in-stone Readers' Rules. Don't let a snarky, crafty, amoral murderer go unpunished if you are writing a mystery and don't plan to bring him back for punishment in a later book...etc.
This has come up because I've been re-reading an old mystery series by a wonderful writer. I read two and in each of them I was reminded that the murderer was someone I really liked. This is ok for a mystery, sort of a good twist, but it also depressed me. One of the times it was the love interest, and I like a romantic subplot to my mysteries, an HEA romantic subplot.
I was looking at the other books in the series and recalled that one of them did the same, the love interest was the murderer...which, when each of the books is written in the first person POV of a female protagonist (different every book, not the detective who is male), makes you question their judgment. All three times they trusted someone they shouldn't have. Thus, again, the depression at the end of a story.
I also read three stories in an urban fantasy anthology. One was quite satisfying on the suspense and excitement and the romance level. Another, by an author I don't read, killed off a lot of secondary characters that the heroine liked -- one of whom she killed herself in something like friendly fire. That's ok for urban fantasy, but, again, I'm a softie and I won't be reading the books with this same heroine. The third was in a world I liked but just an "eh" story. All about bloody vengeance by characters I couldn't really sympathize with. I'll continue reading this author after I hear about her next book, since, for me, her work is "uneven."
So it may be a gray day, and it may be that I'm behind on my self-imposed deadlines, and it may be that I paid a LOT for repairs to my car (long story but I feel burned on that right now, too), and it may be the bad economy that still bums me out, but right now, I want guaranteed cheerful comfort reads. With HEAs. So I won't be re-reading the rest of that mystery series, though I will keep it because the author is a very good writer.
May you enjoy all that you read today.