The Pharisees .. demanded of him a sign from heaven, to test him. And with a sigh that came straight from the heart he said 'Why does this generation demand a sign? I tell you solemnly, no sign shall be given ..' And leaving them again .. he went away to the opposite shore. (Mark 8:11-13)
You can imagine how it could have happened. The arrogant demand for a sign, the eyes betraying the thought: "Nah, don't bother. I know your game. You're a fake: you can't do it." You can also imagine the frustration as Jesus fetched such a deep sigh, jumps on a boat, fleeing for the opposite shore.
How do we pray? St. James tells us in his letter:
If there is any one of you who needs wisdom, he must ask God, who gives to all freely and ungrudgingly.. But he must ask with faith, and no trace of doubt.. (James 1:1-11)So there we have it, in the example of asking God for wisdom: ask, don't demand (and don't test), but with confidence. Why with confidence? Well, God loves you.. doesn't he? By faith, we know: yes he does. So every doubt is is not just lack in confidence: it is a lack in trust.