That link from yesterday about people's beliefs about soul mates gave me a few more thoughts. (Don't worry, I'll be done soon!) The beliefs in the core idea of soul mates--that it is the most important factor in marriage, that there is only one who truly fits the bill, and that this person will appear when the time is right--are so widespread, that it is obvious many Christians must believe them, too. Not only does my experience verify this, but it seems to me often the Christians who are the most adamant at rejecting any whiff of worldliness in their mate-finding habits are most likely to endorse a Christianized version of this idea.
"God will bring the right person in His time." and "Wait for God's best."
Now, we could get into some detailed debates on the revealed and sovereign will of God here, but although we are given many general statements that God will be guiding the steps of those who follow Him, I have yet to find the verse that says God has a One Right Person picked out for us--much less the undoubtedly implied belief if we just wait for this "right person" we will have a better marriage than any alternative.
Actually about the only case I can think of in the Bible where God flat-out told someone to marry a particular person (once there was an open field, of course) it turned out quite badly (see Hosea). And although we can see God directing many marriages in the Bible, He usually works through the perfectly humdrum means used by people who have decided they need or want to find a spouse. (Isaac, Jacob, Ruth.)
In other words, it's not so much that this statement is wrong on its face, it's that it usually seems to be applied in a way that trusts God to work like the mystical fate that leads us to our appointed Mr. Wonderful. Which God never promises to do. He's busy working on our immortal happiness and his immortal glory, which may or may not involve a deep and lasting connection with another mortal.
"It's better to be single than to be married to the wrong one."
Now, if by this it's meant that it's better to be single than to be married to someone who is abusive, unfaithful, or chronically irresponsible, then of course it is true. And if it's meant as consolation for a relationship that didn't work out, it's unarguable.
But if it, as seems more likely, means "it's better to be single than to be married to anyone less than your soul mate," I'm not so sure. Both the Bible and statistics suggest that the bulk of marriage's advantages come simply from having a reliable warm body at your side, to sleep and work with. Unless you're called to singleness, it's probably better to be married to someone reasonably nice than to hold out hope for perfection; who knows--you might wake up some day and realize you married your soul mate after all.