Can (or should) we make life decisions based on our dreams?

I was talking to a girlfriend recently who has just started a relationship with a new bloke. This is the first time she has been out with someone for a long time - she was in a long-term relationship at university, which was sort of her first love, but it ended painfully, and she has barely seen that boy since. That was the last time she had let any man really close to her, she said, but now she was embarking on this new relationship.
But then she told me about a dream she'd had, the night before. She was walking up a long tunnel (I know, quite Freudian), then she came to a sort of underground cafe. She sat down at a table in the cafe, and then a person came in and sat down at the next table. It was her former boyfriend from university. They were both really shocked to see each other, and somewhat scared, because they both knew that this couldn't be a coincidence, but that in some profound and slightly scary way, they were meant for each other, even if they'd both made other plans.
My friend said she'd woken up somewhat disturbed by this dream, because the boy in question was actually getting married in a few months, while she was about to start on this new relationship. And yet here was her unconscious, apparently telling her that she and her ex from an unsuccessful relationship many years back were soul mates. And you can't argue with your unconscious....can you?
So, she asked me, her friendly amateur psychologist, should she listen to her dream? Should she seek out her first love, appear at the church during his wedding, banging the windows and shouting 'Elaine! Elaaaaaine!' (or whatever his name is).
Well, I didn't know quite what to say. But it seems to me, that dreams are mysterious and by no means straight-forward communicators. Even the ancients, who fully believed that some dreams were messages from the gods, also accepted that other dreams could be misleading. Thus Virgil in the Aeneid declared that dreams came from one of two gates or portals. If a dream came from the gate of horn it, not a wet dream, but a true dream, a message from the Gods. And if it came from the gate of ivory, it was a false dream.
But how are we meant to tell the difference? Isn't horn pretty much exactly like ivory? Well,the only way to tell where a dream comes from is to follow its advice. And if it turns out to be really bad advice, then it was probably from the gate of ivory. Easy, eh?
For example: When I was living in Moscow, I went to stay in a famous old monastery, called Optina, in March 2005. Optina is a famous place in the Russian Orthodox tradition, a place considered to have great spiritual energy, a place that's inspired everyone from Dostoevsky to Tolstoy. I went there around this time of the year, back in 2005, to write an article about it. I was, I should add, pursuing a girl at that time, back in Moscow - a Russian-American Jewish girl, who had intoxicated me with her saucy wit and lively eyebrows.
So I stayed in Optina for a few nights, living a most pious existence, waking up at 6am to struggle through the snow to church; eating diced carrots and cold potatoes for lunch (it was Lent); and being given long, mind-bending religious instruction by the Archimandrite of the monastery.
And then one night, I had a dream. In the dream, I was walking arm-in-arm down the street with this sexy young Jewish girl, and then we came across an ex of mine, my first love. And in the dream, we talked for a bit, and then said goodbye, and I walked on happily with the Jewish girl.
I awoke feeling full of the joy of spring, thanking the spirits of Optina for giving me this dream. The dream was telling me, it was clear, that the first phase of my love life was over, and I was embarking on an exciting new phase with the Jewish girl. I went back to Moscow that very afternoon, excited by the prospect of my burgeoning romance.
Sadly, the dream turned out to be from the gate of ivory. The Jewish girl led me on a merry dance for several months, allowing me to make ever bolder declarations of my feelings, only for her to declare that I was a 'short-ass' and she was still into her tall and handsome boyfriend. Curse you, gates of ivory!
I do believe that sometimes dreams can tell us things our conscious minds do not know or cannot face. But other times, they lead us up the garden path. So it's extremely risky, if not outright foolish, to try and second guess our unconscious and make life-decisions based on our dreams. We can only ever see the wisdom or foolishness of dreams in retrospect, when the future has proved them either to be made of horn or ivory. We might use dreams to try and understand our own feelings or wishes, but that's a different thing to using them to predict the wishes of the universe.
Going back to my friend, does her dream mean that, in her heart of hearts, she wishes she was back together with her university sweet-heart? Well, he's getting married, and it didn't work out in the past so it probably wouldn't work in the future either, even if he wasn't getting married, which he is. So she better just deal with it. That's not a dream. It's reality, baby.