It seems the most important factor when measuring how well a country is doing is its economic growth. When a countries growth is = 0% it is seen as a disaster.

For a country with adequate living standards why is it so important for its economy to continue growing? Could it not just stay at 0% indefinitely (or perhaps matched to its population growth) and everyone would still be happy?

One theory that I have heard is that it is purely because of the interest payments necessary on the countries debt? The economy needs to grow to just keep up with its debt repayments. Is this really true?