living sacrifice- but why?

Romans 12:1 (New International Version)
Therefore, I urge you, brothers, in view of God's mercy, to offer your bodies as living sacrifices, holy and pleasing to God—this is your spiritual act of worship.

I have read this verse so many times, but it wasn't until a few weeks ago that I really and truly understood exactly what it meant. Every time I read this I would think, "okay, offer my body as a living sacrifice to God. Got it." and keep on reading the next verses. But I had yet to ask the question why.
Why do I offer my body as a sacrifice? Why should I devote myself to the Lord?

If you read in the chapters previous to chapter 12, the apostle Paul writes about God's sovereign choice to even create us. The fact that He even took the time to decide what color eyes each of us have should make us fall on our face in worship.
God sent His only Son, Jesus Christ, to take the penalty for our sins. And with a simple plea to Him for forgiveness and faith that He is Lord, you can become His child.
Why should we keep ourselves pure for our future husbands? Why should we abstain from sinful desires? Why should we strive to live a holy life? Because in view of God's mercy, of what He has done for us, how could we not?

Romans 12:1 (New Living Translation)
And so, dear brothers and sisters, I plead with you to give your bodies to God because of all he has done for you. Let them be a living and holy sacrifice—the kind he will find acceptable. This is truly the way to worship him.

In His Love,
Jessica