When is quitting a good idea?

I have been going through the podcast guide and I must say this question has stumped me. I know you would tell me not to stay in I don’t know so here I am figuring it out. 🙂 I guess I’m trying to think of the most extreme example, like if my goal suddenly became a life or death situation where if I continued toward my goal someone would die… Yeah I can’t even think of a good example. So does this mean there is really never a good reason to quit? Wondering what your thoughts are on this.