Small Wins

"The answer, it turned it, was simply progress. A sense of forward motion. Regardless of how small.

This is why so many people who don't need more money still create new businesses. It's why others parlay their success sideways to get into philanthropy. And it's why billionaires like Groupon's Andrew Mason and Microsoft's Paul Allen start bands. Even if their subsequent endeavors are small, they can hold depression at bay by making progress on, well, anything.

They don't have to do something bigger or better to be happy. They just have to keep moving.
This is what psychologist Karl Weick of the University of Michigan calls "Small Wins." "A small win is a concrete, complete, implemented outcome of moderate importance," he wrote in a seminal paper for American Psychologist in 1984. "Once a small win has been accomplished, forces are set in motion that favor another small win."

For someone who's suffering from a lack of momentum, discouragement comes in part from a feeling of a lack of control. "Small wins are controllable opportunities that produce visible results," Weick says. And that's all it takes to start feeling better.
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From the article:
http://www.businessinsider.com/psychology-of-success-why-billionaires-get-depressed-2014-9