Economic growth - wishful thinking?

I've spoken before about being concerned that some of my thoughts are naive or ill-informed (ie "is it just me, or.....") but I'm a bit confused about all the talk of growth - and the reliance on it.

As I understand it, a country's economic growth can primarily only come from two sources - greater consumption by it's citizens and businesses (which surely can only come in any significant sustainable measure by an increase in population) or from exports. In fact, I'm sure Obama said in his G20 speech that for global growth, weaker economies should work to become more efficient and competitive so they can export, and stronger economies should be prepared to open their markets for others.

Problem is, it seems to me, the world is a closed system as a whole. If one country is exporting, another must be importing. The net sum of exports against imports must be zero. Therefore, economies that grow through exports must do so at the cost of other economies.

Looking at the state of our country's debt, and that of its citizens, surely much of the growth our own economy has had over the last couple of decades has been at the cost of running up personal and national debt?

All the plans both domestic and through the EU in particular that rely on growth really do seem to be so much wishful thinking to me - or worse, deceit, a fop to the people to delay the day of reckoning.

Greece, for example. It's said that the only hope for the Greek economy, and the very nation, is for their economy to grow. Even after the bailout and debt write-offs, they can't survive, reduce their defecit and manage their debt. How on earth are they going to grow their economy? The only hope I can see for them is to decouple from the Euro, devalue, and be able to exploit their greatest natural asset - tourism, by becoming a destination of choice again because of the value they can offer with a weaker currency.

Come on, put me straight. To my mind, all the strategies for economic recovery should assume no growth. Any growth there is would then be a bonus.