The context is about an unexpected literary success, which likely brings financial gain and professional recognition.
The idiomatic expression "fortune was made" means "I had secured wealth and success." This perfectly fits the situation of an author whose novel turned out to be unexpectedly successful.
Option (a) "days were up" is negative and implies something is ending, which contradicts the positive tone.
Option (b) "chances were good" suggests hope but not a definitive achievement.
Option (c) "ladyluck was happy" is informal and awkward in phrasing; the standard idiom is "Lady Luck was smiling."
Therefore, "fortune was made" is the most accurate and idiomatically correct choice for this sentence.