This is on the inspiration of Expector's Tips on English Usage (1): replace or substitute

The typical beloved prevailing in the literature always replaces the lover with the rival, or some other guy has been substituted for lover.  There is always the lover who suffers. Or again if beloved takes someone in place of lover to the party, again lover is the one who suffers.  

Why on earth the lover is always suffers and the rival is always the one who enjoys the nearness of the beloved.  This is because the lover likes to be smoldered.  Being happy is not nourishing for a lover.  The poetic literature, especially in my native, which is full of the poetry wherein the lover always wails, cries mournfully.  There is of course happiness too when the poet sings the joyful songs of being with the beloved. 

But it is rare to see that a typical beloved replaces the rival with the lover or at least the lover is substituted for the rival. There is slim chances that the beloved takes the lover to the party in place of Rival.