In the story I am writing, the protagonist begins the story already in love with his significant other. They are even set to be married. However, the adventure that pulls the character away, also pulls him away from his love. From then on, they can only communicate sparsely through the story, straining the relationship. Then the hero meets another girl on his adventure, much more sensual, much more alluring. And thus the tug of war on his heart begins. One that lasts for the rest of the story. However, he resists this second female, only to return, transformed, to his original love. His childhood friend and soul mate. But he is changed and gains a new and deeper understanding of his love for her, and love in general. Has this premise been used successfully? I couldn't think of any stories, but I'm sure it's been done.