Pre-excitement?

Can our pre-excitement cause something to not occur?

Maybe it's one of my problems with my understanding of God, but I seem to suffer from the sense that if I become too excited about something happening or an opportunity, it never comes to pass - sort of the feeling that Charlie Brown gets every time the ball is ripped out from under him by Lucy.

I don't suppose that's really God's fault, more my perception of Him.

I do believe pre-excitement can cause something not to occur in the sense that we all of a sudden start acting as if something had occurred when nothing has happened - a sort of arrogance about the future, as if we already know what has come to pass. This sort of attitude can turn folks off faster than anything, and suddenly the opportunity is gone before it even arrived.

But the question I am dealing with far more supernatural than that. When we become overexcited about a future opportunity and act as if it has already occurred, are we usurping the prerogative of God? And if so, does He respond to that by shutting that opportunity off because we are more excited about the opportunity than Him?

Or is all of that as well a function of my own will? Something good possibly happens, and I believe that God must be behind it. Then, when circumstances intervene and it suddenly doesn't happen, I ascertain that I must have become too enthusiastic (and arrogant) when in fact that opportunity wasn't any more likely to happen than the fact that it might rain today.

How do I balance anticipation about opportunities with a realistic assessment of how likely they are to occur?