As for what they would eat the next day, the Israelites had been assured that there would be fresh manna the following day. Our appropriate stress tolerance is to be concerned for just one day - twenty-four hours, at a time. If we take on more than that we may be overburdening the system. There’s nothing wrong with putting some things aside for a rainy day. However, we often take on worries about things that we are powerless to alter or to prepare for today. Such futile worry is harmful.