From time to time I speak to young professionals trying to make their mark on the world in politics, academia, or journalism. The question I encounter the most is this: “What’s the best career advice you give to young people trying to make it.” My answer often touches on the importance of perseverance, because it’s easy to get discouraged by setbacks and rejection. Landing your dream job isn’t easy when you don’t have a lot of work experience, and sometimes keeping it is even harder, at least if you approach your work with the wrong mindset. And many people seem vaguely aware of this. A stunning percentage of Americans live in fear of being fired, data show, and this is particularly true for younger workers. According to one recent Harris Poll, 61 percent of American workers between 18-34 suffer from anxiety over fear of losing their job, compared to 41 …