Vocations are those things that you do not change. You are a son or daughter to your parents for as long as they or you live. You do not choose this. It belongs to you quite apart from any choice on your part. Likewise, parenting is a vocation not chosen but the responsibility and privilege until you or your children die. Marriage fits this idea of vocation. You do not wake up and choose today to be married or not. This estate belongs to you whether you feel it or not. In contrast, you may be a nurse or lawyer or janitor and it these are not vocations but occupations. Work is a vocation but where you work is not. It is a matter of choice. It should be guided by a sense of your skills and abilities as well your training but where you work is not strictly your vocation.
Celibacy is a vocation, a gift, and not simply a choice. We are to remain chaste until married but this single life is not the same as the celibate life. Many have tried to elevate the single life to a vocation but this is an attempt to make sacred what is anything but sacred. The modern idea of the single life is not at all rooted in vow or promise or commitment but just the opposite. It is the ultimate self-indulgent life. That does not mean it is necessary filled with lust but it is self-centered and self-absorbed. The single life is by its very nature unstructured and individualistic. The single life should be subject to all the other marks of the life of the baptized but here the identity is being fudged. The single life is chosen not to engage responsibility but to avoid it and yet without the pursuit of the holiness of chastity or abstinence.
There is a calling either to marriage or to live a chaste and celibate life. There is no third estate of the chose who choose to be single without giving up any desires or indulgences. This single life is a lie and a deception. It is an attempt to sanctify the plain attempt to avoid sacrificial relationship and responsibility for anyone but self. The single who desire marriage and who are looking for a spouse are a different story from those who choose to remain single but still indulge sexual appetite and even have a child but without marriage and without the burden of a spouse. I do not mean to suggest that those looking for marriage should be lumped in with those who cohabit, who enjoy friendship with benefits, who want career and success, but who also want, from time to time, to enjoy the company of another in more than a friendship. In fact, I have grown weary of trying to explain to those who live this self-absorbed life how this is not a vocation or a legitimate choice for the Christian.
I know many singles who desire more than anything to be married. They deserve our kindness and compassion for the special burden borne by their unfulfilled desire. Yet this does not include a wink and a nod at casual sexual indulgence on the way to finding that spouse. I also know many singles who are single by choice, who do not desire the entanglements of marriage, but who have not foregone any of the privileges of marriage simply because they are without a spouse. They have personal pursuits in which there is simply no room for another -- much less a family. But we need to be careful about inventing a vocation where this is none. Individualism and the indulgence of individual desire may require our forgiveness but they do not deserve the covering of legitimacy that vocation gives.