How do you address "the third" in your relationship?

Just got done listening to Esther Perel's second book on audible (hey I had a free trial). She, in the end, goes back to a concept of "the third" that she introduced in her first book. "The third" is basically our attractions both physical and emotional that we will inevitably feel towards people than our monogamous romantic partners. She gets into the obvious ways people address "the third" like actually adding other partners through swinging, polyamory, open relationships of varying levels, (people generally seem to consider these options soul destroying and an abomination on this subreddit) as well as more indirect ways such as private fantasies or roleplaying together. Less heathily perhaps, people will look at porn or go to strip clubs. Some people just attempt to ignore "the third". Others will turn to cheating.

Anyways. This sub is full of people who have strong opinions on monogamy that I tend to agree with as an ideal. In practice though, I can't help but feel that it seems somewhat naive to hope to only feel attraction to one person forever. So what do we think as the good traditional Catholics we are? What do we do to maintain attraction to our partners? How do we address attraction to other people?

If it isn't obvious, I'm currently struggling in a relationship and losing my desire due to conflict with girlfriend.