Something forbade me either to enter or retire, (a) a feeling. i know not how it
came that i was in the presence of imminent tragedy and (b) might serve my friend
by remaining
b.

do you have a picture of the cartoon?

the pronoun reference replaces a noun, but you have to make sure there's no room for confusion.

in the first sentence "her" could be referring to shely or to the sister. the answer there is "shelly called her sister and told her about the new baby."

in the second sentence "it" could be referring to the roof or the floor. the answer there is "since the roof leaks on the family room floor, we need to repair the roof."

misty passage from the question