The only thing that happens is that you eventually compromise and end up with someone who is far short of your ideal mate. you're far short of her ideal as well, but you both stick together because of basic relationship inertia. you may have once had great sex with her, but you don't really remember because you were drunk. for a time, she was just getting herself off with a vibrator while you pathetically jerked off in the shower. but now she's not even doing that, another man is fucking her brains out when she has her "girl's night out" with her "girlfriends." so, you only end up staying together for financial reasons, and because making a big change in your living arrangements is too much of a pain in the ass for you both. inevitably, she'll leave, and you'll kill yourself because you can't stand to be alone after all those years, and you don't know how to replace the girl you settled for.
no, the best thing to do is to remain alone, give up hope, and put what energy you can still muster towards something productive. you'll be a shattered husk of a man, but that's still preferable to not living at all.
No, i just know way too many married idiots who've more or less had that happen to them, and I'm using imagery stolen from American Beauty to elaborate on the hopelessness situation they're stuck in. My brother settled for a dumb cow, and she destroyed and bankrupted him, and now he's garbage. My aunt's husband tried to murder her after they'd built up a successful real estate development company. Another one of my aunts died a broken crackwhore, because one of her boyfriends had gotten her into drugs. Others have managed to salvage things a bit by having weird hobbies, or by buying lots of material garbage. They're all just as empty and lonely as we are. So don't even think for a second that the relationships that you all long after are worth a shit.
As for me? Yeah, I'm lonely, but I've learned that being lonely doesn't mean having to be miserable.