Shoshana Zuboff in Fast Company

Does he ever feel discouraged? "The weight of the environmental problems we face can be overwhelming," he admits. "But 50 years ago, these issues weren't even on the radar screen. I focus on how I can make a difference. There are so many ways to have an impact. I try to make sure I am moving in the right direction each day."

After college, Namrita Kapur spent three years teaching high school in Sao Paulo, Brazil. "I realized early on that making money wasn't enough," Kapur says. "I needed to be doing something I loved and believed in." Her deeply held commitment to sustainable development eventually led her to graduate school for degrees in forestry and business. She followed a winding road, from land management to environmental lobbying to investment banking with a specialization in alternative energy, until she found the job that put it all together. She now helps lead a firm that provides credit to coffee growers certified for organic and sustainable agricultural practices. "I wouldn't be here had I not pursued my values and my dreams about how I want to live my life," she says. "Our work has a profound impact. We have substantive, respectful relationships with the people to whom we make loans. They're at the center of our business model -- we need each other."

Does she get down? "Of course I get frustrated -- there is so much to do! But then I tap into the roots of my values, and that energy sustains me. I recharge myself when I see the fruits of my effort, and I feel hopeful. When there are obstacles, I am pragmatic: I find new tactics, new directions, and take advantage of unexpected opportunities. Optimism thrives on the art of the possible."

As Olson, Kapur, and many other young men and women prove every day, there is a case for optimism:

• Optimists know that change is real. Historical perspective helps. Just think: So many people today are working on issues such as sustainability, alternative business models, or human rights. These were invisible to most people only a few decades ago.
• Optimists measure change one person at a time. If everyone gives up, we're doomed. They look at what can be accomplished instead of being paralyzed by the big picture.
• Life is good when you live from your roots. Your values are a critical source of energy, enthusiasm, and direction. Work is meaningful and fun when it's an expression of your true core. You don't have to settle for work that puts you at odds with what you believe in.
• Optimism makes friends. Finding your own good work is likely to land you in good company. That's a critical ingredient for fun, laughter, and joy at work.

These conversations reminded me that optimism is nourished by practicality. Optimists can celebrate the glass half-full in an imperfect world. Optimism is not the same as idealism. In fact, it may be just the opposite.