Tim O'Reilly talks about the importance of working on things that are important, not just things that simply make money:
First off, though, I want to make clear that "work on stuff that matters" does not mean focusing on non-profit work, "causes, or any other form of "do-goodism." Non-profit projects often do matter a great deal, and people with tech skills can make important contributions, but it's essential to get beyond that narrow box. I'm a strong believer in the social value of business done right. We need to build an economy in which the important things are paid for in self-sustaining ways rather than as charities to be funded out of the goodness of our hearts.
Some of you may end up working at highflying companies. Some of you may succeed, and some of you may fail. I want to remind you that financial success is not the only goal or the only measure of success. It's easy to get caught up in the heady buzz of making money. You should regard money as fuel for what you really want to do, not as a goal in and of itself. Money is like gas in the car — you need to pay attention or you'll end up on the side of the road — but a well-lived life is not a tour of gas stations!