on one's guard

“Nature here is so strong that one has to be on one’s guard to not be absorbed by it,” wrote Dodge.

Government regulation — and confiscatory taxation — neutered the animal spirits of capitalism; the world was a dangerous place, in which it paid to be on one’s guard; Britain was not finished; communism was an evil which threatened the world and stunted the life-chances of those who had to live under its heel.

An Amusing Meeting in Orsera—Journey to Corfu—My Stay in Constantinople—Bonneval—My Return to Corfu—Madame F.—The False Prince—I Run Away from Corfu—My Frolics at Casopo—I Surrender My self a Prisoner—My Speedy Release and Triumph— My Success with Madame F. I affirm that a stupid servant is more dangerous than a bad one, and a much greater plague, for one can be on one's guard against a wicked person, but never against a fool.

Watchful; vigilant or on one's guard against danger or difficulty.

To be on one's guard; to be cautious; to take care; Ð commonly followed by of or lest before the thing that is to be avoided.