I am more than likely about to jinx myself, but I normally don't struggle much coming up with a book title, but I know some writers do. 

It is so important to make sure the title of your book not only matches the book cover, and blurb, but the plot. If your story is about a mermaid, you sure don't want the title of your book to be...A Werewolf's Lost Mate. 

In my opinion, a decent title is also very important.