There was a point when I realized that every rebellious path my "you can't tell me what to do" heart led me down had left me sad and broken. That moment is when I first understood this verse.
Once we have called, our next step is to watch. He has never broken a promise and He is promising to show us great and mighty things we do not know. God finds joy not only in our asking but also in our anticipation that follows. Lets not rob Him of them!