"Skepticism" means not believing everything you are told. "My friend believes in astrology but I'm skeptical about it." The opposite of skepticism is "credulity," believing everything you hear. Someone who is credulous is therefore "gullible." A gullible person is one who is easily cheated (=swindled, duped, gypped, scammed, taken in by, conned) by a liar. Businesses are constantly in danger of being cheated, so It is "unhealthy" for a anyone in business to be gullible. Therefore, any businessperson needs to maintain "a healthy skepticism."

It means a healthy amount of doubt about any area, so investigating the methods or data that was used to make the conclusion. Don't believe everything that people say