This illustration is from Krugman's macroeconomics textbook, it's supposed to illustrate following situation (assuming that it happened for many people):
Conversely, suppose you have a good job but learn that the company is planning to downsize your division, raising the possibility that you may lose your job and have to take a lower-paying one somewhere else. Even though your disposable income hasn’t gone down yet, you might well cut back on spending even while still employed, to save for a rainy day.
In other words, the shift allegedly happened due to bad news about expected future disposable income.
By the way, here is the aggregate consumption function on which the plot above is based ("A" stands for the aggregate autonomous spendings by consumers, "YD" stands for aggregate disposable income of households):
But I don't believe that the plot will shift like this in response to such bad news, it seems to contradict what I learned about microeconomic autonomous spending (I believe that the same must be true for aggregate autonomous spending). It's spending that you just WON'T reduce, they are too critical. You will tap into your savings, you will borrow or ask for charity, you will break the law, - but you absolutely WON'T reduce your autonomous spendings. You don't save money by decreasing your autonomous spending when you hear bad news, you just won't, it's your bare minimum that MUST be spent.
What I imagine will happen instead is that the marginal propensity to consume will decrease, increasing savings of people before the storm arrives, consequently changing the slope of the (aggregate) consumption function.
I understand that it's a textbook, so my reasoning must be wrong and the textbook must be right, but I fail to see mistakes in my reasoning.