"Does not the potter have the right to make out of the same lump of clay some pottery for nobel purposes and some for common use?" Romans 9:21
God's sovereign choice to do what He desires for His creation. Though this is a tough concept to really think about because basically what Paul is saying here is that you could be a common folk. Not exactly what you want to hear. A common use?! Who wants to be that?! Here in America, you are constantly fed the idea that you could be SOMEBODY. But what Paul explains here is that well, you could be somebody in man's terms but you could be common use kind of person, and God chooses who is who.
Not exactly the most soothing message to hear. You are a common person. That's great. But it really is great. If you think about Paul teaches in another book that we are part of a body of Christ a body has zillion of parts, some are visual and big and well known, others are small and in the background. But you need all of it to function properly. So whatever part of the body the Lord has me created for I know that though I may not be of "nobel purposes" I know God has me functioning exactly where He wants me to be. The popular praise song by Matt Redman, "Blessed be Your Name" says it the best, "You give and take away, my heart will choose to say, blessed be Your Name!" His sovereignty is right, regardless of where I fall.
Lord, Blessed be Your Name! You are sovereign and I know that your glory and your will is most important of all.