Let's start with an admission. All of us who do readings, if we are any good, at least at times know what is going to happen. We can argue about whether it's fated by the planets or our intuition is looking at a possible future, and we can hide behind archetypes and psychological complexes, but the basic fact that foreknowledge does occur is still there. And it's not going away.
Now that we've acknowledged the elephant in the living room, I'm going to tell you that it's not really an elephant. Here's what an old-school philosopher (Ptolemy) had to say on the subject:
For, first of all, it is necessary to consider that even for events that will necessarily result, the unexpected is apt to cause delirious confusion and mad joy, while foreknowing habituates and trains the soul to attend to distant events as though they were present, and prepares it to accept each of the arriving events with peace and tranquility.
This is true as far as it goes, but it leads to something we all as readers should consider: our clients worry about the future. That's why they come to us. If we can tell them what's in (or could be in) their future, they can stop worrying about it, and instead think about something more useful and important: what to do about it.