It seems to me that most of the time I am writing to Searching Singles, those Singles who are trying to be okay with being Single but really want to be married or in religious life (but mostly married, really), and not as much to Serious Singles. This is because Serious Singles are somewhat rarer, and since they are generally happy and fulfilled being Single, they don't need to read about it so much. I think.
However, since the internet is not exactly crowded with blogs about the Single Life, it does not do to ignore the Serious Singles entirely.
Who are these Serious Singles?
Well, to shock the stuffing out of you all, I will begin by pointing out that most secular Catholic priests are Serious Singles. There are married priests (especially the ex-Anglican ones) and there are priests in religious life, and that suggests to me that the majority of priests are then Serious Singles, men who can't rely on a wife or a religious order as a sort of emotional/social/financial safety net. Ordinary priests don't take a vow of poverty, which means that they are often very poor indeed. It's a bit scary, sometimes, thinking of how hard secular priests work for how little money. And with fuel costs rising and with priestly dependence on their cars---eeek!
What Serious Single priests do have is a pulpit, so I wish they would use it more often (e.g. once a year) to talk about the Serious Single life, and not just the priesthood. There are a lot of devout men who, for various reasons, can't get into the seminary or are chucked out of it and (often for the same reasons) can't get married either. They don't need another homily about the priesthood, as important as such homilies are. They need homilies about how it is tough to be male and Single, but how such a life has its joys and opportunities, too. The married people can lump it one or two Sundays out of 52; they get oodles and oodles of attention.
Speaking of lay Singles, there are men and women who feel so devoted to their professional calling, like medicine or spreading L'Arche communities throughout the world, that they don't see how marriage fits into this. They deliberately make choices to travel to poor countries or live in L'Arche communities or do other things that makes it very difficult to find (or be found by) somebody to marry. They are seeking them first the Kingdom of God, and God bless them for it.
Then there are men and women who are not sexually attracted to the opposite sex, and therefore would find it very weird, uncomfortable and fake to get married. This has not stopped all such men and women, of course, from contracting disasterous marriages, but people of integrity tend not to marry innocent people as some sort of disguise.
Devout Catholics who are not attracted to members of the opposite sex, therefore, live their lives (or try to live their lives) as chaste Serious Singles. Sadly, just by being who they are, they risk criticism both from gay activists on the one side and from overly wound up fellow devout Catholics on the other. To quote my Inner Child, this sucks. If a Serious Single is Single because s/he isn't attracted to members of the opposite sex, that is his/her own business and if s/he don't feel like talking about it, leave him/her alone. Coming out of the so-called closet is not the human equivalent of a butterfly bursting out of a crysalis. It is not actually the eighth sacrament.
Then there are Serious Singles who have physical and psychological issues that make it very difficult for them to get married and have babies. There are some incredibly unselfish people who deliberately say no to marriage and babies so as not to pass on a genetic disease to another generation. I am not sure I agree with such decisions, since all things--like healthy babies regardless--are possible for God, but that is the decision of the Single person.
And then there are the extremely mentally ill and those with developmental disabilities so severe that although they can, of course, have friendly relationships with their families, carers and others in the community, they cannot take on the responsibilities inherent in marriage and parenthood or in religious life. These, too, are called to the Single life.
(By the way, there is a religious order for women with Down Syndrome, so developmental disabilities alone do not preclude religious life.)
Finally (although it might not be finally), there are Widows and Widowers, who have lived perhaps long lives as married people, and are done. The order of Widows is a very old one in the Church, and heaven knows what the Church would have done (and would do) without the activities and prayers of Widows all these past twenty centuries. Either B.A. or I will be Widowed one day, and I wonder what a job he or I will make of it.
Anyway, I am sure there are many more categories of Serious Singles, so if you belong to one, feel free to name it in the combox.
The Catechism, incidentally, says that Single people are especially close to Jesus's heart (CCC 1658).