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")
I don't think it is pedantic at all. A prepared mind is exactly what is needed to take advantage of opportunity. Prepared mentally denotes a state of mind where you are actively looking for opportunities and that allows you to notice them. It is an attitude, really. Not unlike being a Stoic is an attitude on gratefulness of life and acceptance of death.
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