If households and firms increase the level of private savings because they become pessimistic about the future, then:

If people are saving their money because of pessimistic feelings about the future then it will have an impact on current spending in the economy. When people are saving instead of investing money or purchasing large items such as homes or vehicles than the businesses in those markets are affected. For example, if there is no one buying new houses, then builders will see a decrease in work and the companies that provide building supplies will be affected. The people in the companies will also begin spending less as there is less work and less money to go around which also affects the economy on a large scale.