Your writing should be either:
I struggle with this though.
I want to write about what I like – what I find interesting.
But beyond my own interest, where is the long-term value?
Where is the audience?
Keeping within the scope of these two guidelines is great practical advice, however.
For both of these uses are timeless.
One of the best pieces of advice I’ve gotten as a creator was from a successful writer who told me that the key to success in nonfiction was that the work should be either “very entertaining” or “extremely practical.” Notice they didn’t say, “Should be very fulfilling to you personally” or “Should make you look super smart” or “Capitalize on some big trend.” Those concerns are either secondary or implied. It’s better to be focused on those two timeless use cases of enjoyability or utility.
-Ryan Holiday, Perennial Seller