Examples
Example 1
My girlfriend I couldn't see each other through all the fog in the haunted swamp.
Here, the reciprocal pronoun is used because neither the speaker nor his girlfriend can see the other person. They can't see the ravenous werewolves that are slowly approaching either…
Example 2
Tiffany and Henrietta complimented each other on their prom dresses.
In this example, the reciprocal pronoun is used because both girls are giving compliments to their BFF.
Example 3
At high noon, the cowboys stood in the street and stared one another down.
In this case, the reciprocal pronoun is used because the cowboys are engaged in the mutually macho act of staring.