I have always found that matching "fickle" and "fate" together was close to contradictory. "Fickle" is about instability, likely to change, unpredictability, whereas "fate" is about predetermination and unavoidability. To describe fate as fickle seems to say that you don't believe in fate, which is fine, but in that case why use the phrase?
I realise the above is not necessarily accurate. It is not completely unreasonable to match the words because the results of a predetermination may indeed appear fickle to those that experience it. I may throw the dice to see which of my characters to kill off, but if I really believe in fate then I believe the fall of the dice has already been determined. ... Still, the words feel like an unnatural pairing