The title makes no sense with the question - Choosing each other daily is not denial - that is devotion. Devotion is intentional, it isn't an emotion.
When things are good, monogamy probably does feel effortless. I’m more interested in how people handle it when that effortless stage wears off. For some, staying devoted becomes an intentional act rather than just a feeling. That’s the bit I think most people gloss over.
Not sure it gets glossed over - maybe in movies, but there is a whole world of relationship research that discusses that no relationship can be based on a feeling, any solid base is intentional.
IME, ease in that intentionality in relationships comes and goes and importantly can return, often influenced by the environment, experience, as well as intentionally.
I'm more than two decades in and marriage/monogamy is easier than ever, far easier than the start. It is essentially effortless at this point as what we've built habits and woven our stories and lives together in a way that's really enjoyable.
The hardest part of my marriage was about 10-15 years in when we were dealing with multiple loved ones going through terminal illnesses, the care responsibilities of both that and young children, managing the dying and deaths of loved ones with young children & culture clashes within the family on how dying and death should be managed with children and on top of that, I was in my late 20s and early 30s (married at 18), and surrounded by people who were unhappy with whatever situation they were in, wanting more, and sadly had this idea that I think media fuels that if we're facing struggles in some area of life, then there must be an issue with our main relationships as well. I cannot tell you how many times during that time period I had unhappy people, women particularly, telling me that the reason I felt stressed had to be my marriage and/or my husband, and how often I had people unsolicited and with no knowledge of my relationship, who I never discussed my relationship with at any point beyond them knowing I was married with kids, recommend divorce, giving up men, and/or polyamory in various flavours. It ate at me when I was at my weakest. It was nothing in my marriage that was hard, it was the experiences going on around me in those hell years that made life in general hard, and those voice pushed the lens onto my marriage in a way that at times made it appear so.
I came out of that by changing who I was around, working through the losses in my life - both literal in the deaths of loved ones and in those relationships that once really mattered but turned out to be harmful - and intentionally focusing more on my marriage, my home, and relearning what I actually enjoy, not the things that other people told me would make me happy that repeatedly failed.
Now in my 40s, I've changed careers twice since then, I'm mainly around people who are fairly happy in their situations, whether it's happily single or partnered up, and compared to being in my 20s, it's really not as big part of our conversations. My oldest is in his twenties, and three other kids in their teens, I'm no longer in the high stress of little ones or caring for the dying. It's little wonder marriage is a lot easier now.
And really, my early marriage was filled with the stress of immigration, kids, and young adult life, and seeing my own adult children at those ages - I absolutely have no desire to be back at that, even with all the lovely emotions and hormones, life was hard times, which pushes at any relationship - what I've built in the mean time with my husband and wider loved ones is so beyond what young me knew was possible. I'm quite happy to intentionally pick devotion.