Read the entire thread before venturing a reply.
Been in many relationships. Remember the names of everyone I've ever had sex with, and miss most of them, even the ones who were really really bad news. On speaking terms with about 50% of the rest, consider them among my best friends. Most of them (including those I'm not still in touch with) I'd consider way-eligible for new-again rels if they were open to it. Really really good people and I love them.
Never been married, never will be. Only once promised exclusivity, retracted it about 15 days later. Can't recall any time ever in my life that I wanted to be married. Very short period of time age 17-19ish when I might have gone for it for lack of having thought of it one way or the other, but it would not have occurred to me even then.
My reason in short: not exclusive, not monogamist, not inclined to promise what I'm going to do or going to feel.
Marriage is foreign, weird, and to me stupid and disgusting. Incomprehensible.
My current rel is my longest-lasting. Neither of us was inclined to pack it in when the initial obsessive passion of being-in-love went away, and we stayed together as a companionable loving couple, and might well stick together until one of us dies. Love, as a different thing from "in-love", persists, and we care about one another and take care of each other. She's theoretically monogamous, I'm not. We both miss being "in-love".
I keep hoping she meets someone and it happens for her, and me and her stay connected throughout and are there for each other when it's over. With or without him also still being there for her when it's over.
It could happen to me instead. which could be far more destructive to what we have: I could fall in love with someone ("in-love"). Get obsessed, etc. Damn, that's delicious, and I do miss it! Would I risk losing the long-term rel I've got for that? Maybe. Can't promise otherwise. Never did promise otherwise.
How could anyone? It's a passion for which folks have sacrificed everything for a momentary taste! We are so wired. I would never contract to forego it. To do so would only be to make a vow that I would break. Are married folks who do the vow-thing different? Mostly, no. Those that are? Not happier, I'll warrant.
Marriage is a relic. Commit to the persons who are your co-parents, for the life of your children. Don't confuse it with other (erotic, romantic) commitments. Commit to love, passion, the person for whom you feel it...for as long as you feel it. Be nice to them when it's time to go. Cope, as astonishlingly painful as it is, when for them it is time to go and you weren't ready. Know, going in, that there is always the risk that you will be left, and will hurt, and it will hurt like no pain you've ever known before. Accept that, as part of being human. No religion, no vow, and no protective institution, can protect you from that. (They may, under some circumstances, most of them belonging exclusively to the past, preserve the official monogamous relationship, but what you retain is a hollow shell).
Single? I was born this way. Genuine transcendence of single indiv identity is via spirituality, not marriage. (I am We who are, and, beyond that, That Which Is, and to the extent I "get" that , who I am does not need to die with the death of me as an individual). Aside from that? I was born individual, and I will die as an individual, and so shall you. If you don't like being alone, transcend indiv experience; there's no permanent solution in romantic passion. Sorry.