Some people believe that there's one person in this world who is meant for them. They call this phenomenon by many names, "the one" and "soul mate" among other things. There are people who believe that this phenomenon does not exist. I'm of the former.
There has to be something said for having a connection with someone. I don't mean a lusting for the other person. I mean the kind of connection, that even after ups and downs, fights, lapses in communication and all other hardships, that person still gives you butterflies with just a look. That person still can make you smile with a text that isn't even one line long. A connection isn't just physical, it's not just the fact that this is the person you want to look at every day til death parts you, because let's face it, hair starts to grow in odd places, body parts sag and pudge sets in after a while. A connection transcends the physical. Don't get me wrong, the physical is a very important factor, without it, in my humble opinion, you're just friends. And while (as someone said to me recently) relationships have their ups and downs, sometimes you want to jump on your partner, and at others you have the proverbial 'headache'; you shouldn't have to be praying to your god to get you through the sex without your gag reflexes coming into play, or feeling violated.
Maybe there's more than one "the one" and I'm still pretty young, but I've only ever experienced it once, and I'm still experiencing it. I have met other people, nice enough men, treat you decent, have a sense of humor type guys, but lack the spark you get from that "one". Forgive me for being demanding or unreasonable, but I want all the bells and whistles if I'm going to do forever with someone. I have no intentions of settling for ok just because great isn't available to me at the time. I'd honestly rather be alone than be unhappy, settling and becoming more and more resentful of him and myself as the days go on because what, I decided to stay with a person just because all my contemporaries are settling down having kids and getting married.
Happy isn't mythical, happy is out there, we just have to take it and run with it when we find it, and for me to be truly happy, I have to have my 'one'. As for the 80/20 rule. Sure it exists, but be forewarned, sometimes 20 can outweigh the 80. What I mean is that you can write your list of pros and cons, you can come up 80 pros and 20 cons and think ok that's a great reason to be with someone, but if the happy doesn't come to you with that person, no amount of pros will ever sate you. And if the happy doesn't come with all the pros this person has to offer, on some level you know this isn't the 'one'