For example...
Spoiler
I was doing the nettlebane quest for that lady in the temple of kynareth in whiterun. I figured it was just something along the lines of "go get this weapon and help me out with this tree" (admittedly I did not pay too much attention to the dialogue, so perhaps I misunderstoof). It was all fine and dandy but when you go to get the sap from the tree, the people in the sanctuary beg you not to hurt the tree. That was it for me - I didn't want to be a [censored]. However, I couldn't just go back and tell the priestess " I won't help you anymore" nor did I think killing her would be justified...
What is there to do in that situation? All I thought of was abandoning the quest, but I hate leaving things unfinished...