There are many "titles" (Dr, Mr, Mrs, Miss) or descriptions (brother, sister, son, daughter, boyfriend, girlfriend) that may or may not apply to us, but these are all only in submission to the most important descriptor of our life - that of being a Christian. Being single describes me only after my being a Christian and a woman, for while salvation and gender do not change, status can change several times throughout life. Thus, it should also not define our life, but instead be an aspect of, or, as Paul calls it, a gift.
As we know, all gifts come from God, and have a purpose, whether or not we know what that purpose is. So, all we can say for certain is if we are single, it is because it is God's will for us Right Now. Now, I know that I have heard (and perhaps, at times, myself thought) that "God will not give us a spouse until we are content with being single". While it is certainly important for us to be content with our position in life, thankfully God doesn't base His gifts to us on our work of being content - singleness and marriage are both gifts, not obtained from our own works.
In much the same way, our usefulness in the church is not contingent on our marital status either (isn't that a relief?!) - each of us, as part of the body of Christ (married or single) has a unique and important purpose, that is shown in how we serve God. That said, we should be diligently at work in the church, serving others, seeking God's plan for our lives (while we may be waiting for God's man for our life) by being active in His kingdom.
One other thing that is helpful to keep in mind is this: we don't know all the circumstances! Because we have no idea what the next year, day, or even hour will bring, we must trust and have faith that God knows best; and, that perhaps He is trying to teach us something even greater by not sending us a spouse at this point in our life. We must not expect Him to work by our own time table, and remember that God's "silence" in this area is not necessarily "No" - it may be a "Wait on Me, Trust Me, that I have your best interests in mind". Would God withold blessings from His precious children without good (perfect, actually) reason?
In closing, here is something that C.J. Mahaney said that really stuck with me:
"Your greatest need is not a spouse. Your greatest need is to be delivered from the wrath of God - and that has already been accomplished for you through the death and resurrection of Christ So why doubt that God will provide a much, much lesser need? Trust His sovereignty, trust His wisdom, trust His love."
- Written in reflection of Carolyn McCulley's chapter "Sex and the Single Woman", taken from Sex and the Supremacy of Christ, edited by John Piper & Justin Taylor
"As each one has received a gift, minister it to one another, as good stewards of the manifold grace of God." - 1 Peter 4:10