This passage seems a little strange; Jesus is talking about eating flesh and blood. We see here that some of Jesus' disciples leave him because they're not able to comprehend what he says in these verses. When we look at verses 68-69, though, we see Peter's response to Jesus' teaching.
Simon Peter essentially says that he's going to stick with Jesus even though he doesn't understand what Jesus had been saying. It wasn't that he understood what Jesus' words meant or even that he knew exactly who Jesus was. All he knew was that Jesus had the key to something greater, and it was to this that Peter held on.
The reality of faith is that we're going to doubt, but we can hold on because there's something more there for us.
Jeremy explained to us tonight that maybe doubt is a part of faith. This is Peter's example in this passage: he brings the doubt and the faith together. We can be honest about what we don't know and don't understand, and Jesus is still with us through that.
It's in our struggle and in our doubt that we can become more confident not only in God but ourselves. It's important, though, that when we have questions that we engage with it and take steps towards understanding. That's how we love God more and find our place with Him.