I know the meaning of this phrase: One should not assume the outcome of some activity (e.g. a sports game) until it has actually finished.
I'm curious as to whether it would more likely be used when
- the speaker refers to an assumed favorable outcome that might turn unfavorable:
"The Giants are going to win this game, no question!"
"It ain't over till the fat lady sings."
- the speaker refers to an assumed unfavorable outcome that might turn favorable
"Might as well go home, no chance the Giants are going to win this one."
"It ain't over till the fat lady sings."
Or does the phrase apply to both situations equally?