Iron rusts from disuse; water loses its purity from stagnation... even so does inaction sap the vigor of the mind.
— Leonardo da Vinci

Curiosity is one of the permanent and certain characteristics of a vigorous mind.
Samuel Johnson vigor quote

Action is the highest perfection and drawing forth of the utmost power, vigor, and activity of man's nature.
— Bishop Robert South

True wisdom for a general is vigorous determination.
— Napoleon Bonaparte

The love of life is necessary to the vigorous prosecution of any undertaking.
— vigor quotation by Samuel Johnson