In managerial accounting Standard costs part,

In the text book, It says that standard costs has the potential problems that "In some cases, a favorable" variance can be as bad or worse than an unfavorable variance."

"Just meeting standards may not be sufficient; continuous improvement may be necessary to survive in a competitive environment"

SO what is this "In some cases, a favorable" variance can be as bad or worse than an unfavorable variance."

Can you explain with example?

How favorable variance can be the worse than an unfavorable variance?

I want to know exact example and explanation in this managerial accounting part