I can only speak from my own experience. I had a few relationships in my mid 20's and 30's. None of them lasted more than a year and a half. Like others, I was cheated on my every single one of them. I'm a huge proponent of monogamy, but I realize that it doesn't work for everyone, and my husband and I have an open relationship at the moment. It was a compromise.
Having been single for so very long, my biggest personal road block was changing my mindset from being a "me" to a "we" and it's something I still struggle with at times. I'm independent. I like to do things my own way, so learning to compromise was a challenge at times.
There is always someone with a bigger, harder cock, and a sexier body, but I have a man who always comes home to me. He's someone I can depends on, and I'm loved in ways I never experienced before. I'll take that over any Tom with a hairy dick any day.