This is from the SQLite creator D. Richard Hipp who is always worth reading, but, I'd like to recommend reading what TCL's creator John Ousterhout has to say.
His article on threads from 1995 was highly influential on me, and I remember it to this day. More recently (2018, revised and expanded in 2021), he published a book on software engineering practices called A Philosophy of Software Design which is, in my opinion, the best in its category.