I believe that we have free will in just about everything except our own salvation and things that are specifically commanded (either a "do this" or "thou shalt not").
So...I disagree wholly with the idea of "THE ONE" as if there is one person out there that is God's hand-selected mate for us. That is more along the lines of "fate" and fate and faith are very different things, fate being far more pagan in nature.
I just don't find the concept of "THE ONE" taught in Scripture. The cloest thing to it is Abraham's servant's prayer regarding Rebecca and while that is a beautiful story and historically accurate, I don't think it serves as a model of how all Christians must select a mate. Any more than I think that the way we should determine if God wants us to buy the white house in the suburbs or the yellow house in the city is by laying a lamb's fleece out on the lawn over night and checking how wet it is in the morning.
It's a big mistake to take these historical Old Testament stories about people who did not usually have the indwelling of God's Holy Spirit (something all Christians have) and believe that this is
the way God wants us to do things...not while He has laid down His precepts and commandments to us in the clear black and white of Scripture.
What
is important is for Christians to view mariage and the selection of the mate as something that we need to apply those precepts and commandments to. God tells us not to be unequally yoked...is this man a godly Christian man? If not, then we should think twice before marrying him.
God tells us women that we are to submit to our husbands...is this a man to whom you can submit? If not, then save yourself a lifetime of frustration and look further afield.
Is this a man who wants to raise his children in the nurture and admonishion of the Lord? If not, then how can you reconcile yourself to follow out your own commandment to raise up your children in the way they should go, if your husband is undermining your teaching?
I was single for quite some time and during the time I was single, I dated a number of men. Almost all were Christian (didn't go on any 2nd dates with the non's) and almost all were godly men. Of the men that I dated, I can think of about 5 who would have made very godly husbands for me...husbands that I could follow the commandment to love and submit...
and I don't think God would have cared which one of them I married. Oddly enough, the man I did wind up marrying was the least spiritual and least "Christian" of any of the men I dated. He was a believer...but hardly a solid man of faith...and yet we've been happily married for almost 14 years now (our anniversary is a week from Tuesday). God has changed him and he has indeed grown into a solid Christian man, a good husband and father.
As for God just telling you so that you don't waste your time...
that would be nice for God to do in all kinds of situations, but I believe God allows us to work through these things so that we can strengthen our faith and be more mighty.
As opposed to just lazy, couch potato types. It's harder, but ultimately more rewarding.
Besides, never think of any relationship as a waste of time, even those ones that don't turn out. Each relationship will add to your experience, your understanding, your faith and ultimately affect who you are as a person. God can work the experiences we have in all relationships, good or bad, to our ultimate good.