John Mauldin, who is one of the people I listen to on economics and the economy, has written a letter to his kids: "What does Greece mean to me, Dad?" It's a bit long and well worth your time.
I will note, however, that I do not completely agree with him. John is a serious optimist; he believes that we will pull through this as an economy, because we always have before. I believe he is substantially discounting the fact that our economy is much less "free" to do the things that need to be done (in terms of debt reduction and new economic activity) than ever before in our history.
Remember, past performance does not guarantee future returns.