"Old Saying Describe Limits and Balance" by Susan Pearl

That's the straw that broke the camel's back.

That was the apple that upset the apple cart.


Why would one lightweight piece of straw break a camel's back?
It means that the camel was already loaded at a full load, maximum weight capacity and, maybe, even over the weight capacity limits for what a camel can carry.  If more is added to that maximum, even if it is a little bit at a time, it will exceed the strength that the camel's back can support.
With COVID-19 things keep adding on top of each other and a support system has to be strong enough to handle the weight of it all.  Social distancing, washing hands and staying home adds to the strength of the nation's support system by lessening the additional weight of having more COVID-19 cases.



How could one apple upset an apple cart?
The apple cart has to have properly balanced weight distribution to not tip over.  When putting the apples in the apple cart the apples should be placed evenly and not be all at one end or the other.  If the apple cart has the apples all at one end then just tossing one more apple could be the apple that upsets the apple cart.  With COVID-19 there has to be a balance of how things are handled to restart the economy.  Practicing social distancing, washing hands and staying at home gives more balance for things to level out allowing the economy to reopen as safely as needed.  To do our part of bringing a balance we have to separate ourselves (have distance) from the virus.