Imagination v. Reality

First, let me set expectations for what this post is about.  I'm not talking about the "I'm twenty pounds lighter and about to get a starring role in a major Hollywood production" kind of imagination.  That's fun and all, but first, that's not where my imagination goes and second, like I said, not that kind of imagination.

I'm talking about imagining reality and then living that reality.  We all do it every day.  We have to, otherwise we wouldn't be able to plan for anything.  We imagine the series of events unfolding and figure out whether they will get us to the desired end state or not. 

"If I leave work at 4 o'clock instead of 4:30, I will gain ten extra minutes because the traffic will be lighter, which means that I'll get to the grocery store by 4:15, grab a few things for dinner, then rush to the childcare center and still make it home in time to make dinner before it's time to work on homework."

Imagine the reality of all those steps and then live them.  And you have some basis for that kind of imagination because presumably you've left work at 4 o'clock instead of 4:30 before and presumably you take the same route to and from work and you know the lines at the grocery store, etc.  There is a series of previously experienced bits of reality that help you construct that imaginary chain today and lead you to have a certain level of confidence that your imagined reality is not all that different from the reality you'll face when you get on the road at 4:05 (because we all know that you'll never actually leave at 4 o'clock... that's just plain fantasy).

But what happens when we try to imagine a reality that never previously existed?  What if you try to imagine what it would be like to do something you've never done before? And what if you have to agree to doing it based solely on your imagining of that reality?  What then? 

What do you rely on to gain a level of confidence in those imaginings if you have no support for them from reality as you know it?

Or worse, what if you are imagining a different reality from one you've already faced?  Which do you trust?  Your new imagined reality or the one that you've already lived through?  Where do faith and experience cross swords?

And when they do, who comes out on top?  That's what I'd like to know.