From Jugglers at the Border, by Robert Fate, third in his series about Kristin van Dijk, aka Baby Shark, a young woman who is a pool hustler and private investigator in 1950s Texas. Her partner and mentor Otis Millett delivers this line about being a detective, but it works just as well for writing.
One of the (many) great things about this series is that Fate knows what Texas was like in the pre-feminist ’50s. Kristin, Otis, and their friend Henry, who is Chinese, are all marginal people — like all good detectives they live out on the edge. Unlike Sam Spade, though, who seems to trust no one, they make their own community.