My Catholic upbringing, such as it was (it took place in an old-time Catholic school with mostly priests and sisters, I didn’t have a Catholic home), taught me that “it’s not what you want, it’s what God wants”. Nil sine numine was the unofficial school motto. You can want, and want, and want, all you like, but in the end, that has absolutely nothing to do with anything, if God wants something different for you. If God wants you to get married, it will happen. If God wants you to go into the priestly or religious life, He will let you know. “Back in the day”, many people went to the seminary or convent, stayed for awhile, and either finally “just couldn’t do it”, or were told by the rector or Mother Superior that, regardless of what the seminarian or novice wanted, they just didn’t have a vocation. In either case, the Voice of God was clear.
And if nothing at all happens, or there is some kind of extrinsic or intrinsic prompting towards it, you just stay single. Our modern society is a pretty harsh, Darwinian place when it comes to finding a mate — many people of either gender have near-impossible standards for finding a mate (money, appearance, personality, etc.), and it’s not at all unlikely that some will remain forever single because “nobody could ever quite measure up”. And some people have afflictions that make finding a marriage partner more difficult than it would otherwise be — personality disorders, handicaps, homosexuality that just won’t go away, and I hate to say it, but sometimes there are appearance issues. It doesn’t seem fair, but it’s just the way it is. Fallen world, fallen people.