There is no magic fairy dust you can sprinkle on an economy to make it grow. To increase GDP you have to actually produce more. That's why it's called gross domestic product.

Therefore—and I'm oversimplifying quite a lot here—a recession is basically a decrease in production (as, normally, population doesn't decrease). Two clear implications emerge: The first is that if you want the economy to grow, there must be an economic environment that is friendly to increasing productivity.

Productivity growth, unfortunately, is slowing down in much of the developed world and there's no reason to think the trend will change soon.
 
Let me offer a few rather disconcerting charts showing the continuing decline in productivity and major shifts in demographics that are worsening the situation.