Joy in God - Not in Goods
What do they do (those who do not want to know that we should rejoice and glory in God) but sadden, disturb, and make themselves impatient, not because adverse and sad experiences come to them but because when they do come, they take the foolish attitude of not looking to God but to their prosperity and comfort? So they flee; but they do not escape, because they do not flee whither we must flee. Therefore the entire cause of every case of sadness is the unwise craving for joy and glory. If the heart did not cling to that desire, adversities would effect nothing. Therefore the proverb is very true;...(The world is ruled by opinons), and conditions are what a man thinks they are.
(What Luther Says - p. 690, 691 - para 2140)