Perhaps pedantic, but "prepared mind" includes your meaning. Prepared may mean being equipped with a skill that meets the moments, but flexibility, acceptance and optimism are also skills of a prepared mind.
It's why the quote has survived since 1854.
> "dans les champs de l'observation, le hasard ne favorise que les esprits préparés" ("In the field of observation, chance favors only the prepared mind")
https://en.wikipedia.org/wiki/Louis_Pasteur