As Christ followers, God has called us to live by faith. If you think about it, the whole notion of "I have to see it to believe it" is really an issue of control. "I want to be in control of my life and so unless I have proof that something is real and true, then I can't accept it. I don't want to act in extreme ways, ways that seem contrary to what would be beneficial to me, unless I have proof that it's going to pay off in the end."
On the contrary then, living by faith is surrendering control. "Even though I can't see it, taste it, touch it, hear it, or smell it, I believe it to be true. Even though it may seem extreme, counter-cultural and it may not make sense to me, I accept it because God says it's true." It's learning to let go of control and believing that God's thoughts are higher than our thoughts and his ways are better than our ways... it's believing that he's big enough and strong enough to order and direct our steps. It's learning to live life his way instead of our way.
So what areas of your life have you been clinging to control? What things do you need to surrender to God? In what ways do you need to begin living by faith?