How could Jacob wrestle with God if no one can see God and live?

Is this a contradiction? Or am I missing something. It seems strange to think one can "wrestle" with God. [Genesis 32:30 (NIV)](http://www.biblegateway.com/passage/?search=Genesis%2032:30&version=NIV) : >30 So Jacob called the place Peniel, saying, “It is because I saw God face to face, and yet my life was spared.” [Exodus 33:18-20 (NIV)](http://www.biblegateway.com/passage/?search=Exodus%2033:18-20&version=NIV) : >18 Then Moses said, “Now show me your glory.” 19 And the LORD said, “I will cause all my goodness to pass in front of you, and I will proclaim my name, the LORD, in your presence. I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion. 20 But,” he said, “you cannot see my face, for no one may see me and live.”