The worst thing?
The decline of the Gothic market mentioned above. I’d written 7-8 of these romantic suspense stories, with steadily growing advances and sales. Then the bottom dropped out. I wrote another gothic before I realized the problem, then did a paranormal mystery suspense tale, a murder mystery, a light historical on the order of a Georgette Heyer Regency novel, and a contemporary romance. Nothing sold. The dry spell lasted so long that I thought it was the end for me as a writer.