to build on what Sue and Ann said, there is not just one person to whom you could marry in your entire life. There may in fact be two at the same time, and you have to choose. The idea of the soul mate is pretty terrible. By this I mean that there is one person out there with whom you would be completely compatible, and if you find this person your troubles are over. Not true at all. Any relationship involves work!
The following are my thoughts- comments welcome! Inside of our call to Chastity is this ability to become a "versatile lover" we'll call it- the ability to interact with Charity, truth and great romance to a wide variety of people. In becoming more like Christ we are able to overcome both our sin and the sin of others, making it easier for Christ to match us up. Christ will lead you to a person, and give you the opportunity to love them. At this moment and place, that is the one!
If you do not take the opportunity they will eventually cease to be the one. If you do take the opportunity as a couple you choose to move forward in God's plan, and you move in God's Spirit. The Spirit will sometimes give you specific directions, but more likely the Spirit provides a "space" for us to discover and grow in each other. The Fruits and gifts of the spirit- Joy, peace, fortitude, wisdom, etc are not usually directions but rather virtues or states of being that allow us to be fully our self. As long as we stay in this space we have both freedom and safety. In growing together in this Spirit that we each change and the couple with the Spirit becomes the image of the Trinity, which is God's plan for us.
Of course from God's point of view of looking at creation from eternity, there was always only the one.
Peace in Christ,