Arabian horses are trained rigorously in the middle eastern deserts. The horses must learn to fully obey their master. This obedience is tested by depriving the horses of water for many days and then turning them loose near water. As the horses get to the edge of the water, and just before they drink of the much needed water. The trainer blows his whistle. If the horses have learned to obey they turn around and come back to the trainer who then gives them as much water as they need.
The trainer knows what his horses need and will not allow them to die of thirst, but they must trust him. God knows what His children need and wants to supply it, but we must trust and obey Him.