obedience

I was listening to the radio while driving home today. Usually, I have my iPod plugged in, but the battery is running low, so I am listening to the radio until I remember to bring it in and charge it. Redeemer, by Nichole C. Mullen came on. Which is kind of odd, considering it was on this morning when I was driving to work. I sang along, and thought about the words:

Who taught the sun where to stand in the morning
Who told the ocean you an only come this far?
Who showed the moon where to hide 'til evening
Whose words alone can catch a falling star?

I know its not the main point of the song. But it got me thinking. God is really really powerful. He made all of nature subject to Him. Why didn't He make humans, His greatest creation, with that same attribute? Why did He give us the choice to be subject to Him? I feel honored that He grants me that choice, when He could so easily control me. I mean, He speaks, and the universe goes into motion. No complaining or dragging of feet, it just goes. So why do I struggle with obeying Him? You would think I could learn a lesson from the ocean's waves, constantly falling where He instructs, no questioning or doubts. Why is it so hard to obey?