Don't believe all you're told
Years ago, I joined the site Writers Bureau. A lot of writers have good things to say about the site, but not me, the harassing I got from my "tutor" almost stopped me from writing.
He told me the hardest market to sell in is the US Sci-Fi market. But, I am sure I cracked that market with sales of 700 e-books for my series Forgestriker.
He told me my writing would never sell, and that he had no idea how/where to pitch my stories. I proved him wrong; I found my market at Barnes & Noble; I suppose he should know what doesn't sell, after all, he spent over 20 years trying to sell his second book - and I bet he is still trying.
Other than my 11th sale of the month, the sale of Avenging Angel means much more to me, because it's the first sale outside the series for months.