As I was taught, with verbs and adjectives, when you want to express an excessive degree, you simply attach 「すぎる」 to the stem of the word, as below.
However, when it comes to negative forms, there seem to be cases where 「さ」 is appended before 「すぎる」, and cases where 「さ」 is not.
For example, I have recently heard:
When is this 「さ」 needed? Is it perhaps optional only for verbs? In the case that it is optional, is there a difference between having and leaving out 「さ」?