The Word of God is to your spirit as bread is to your body. When your body feeds on physical food, it produces a physical power called strength. When your spirit feeds on the spiritual food of the Word, it produces spiritual power called faith.
And just as you can't eat one meal and then feed on the memory of it for several weeks, you can't just remember what the Word says and stay strong in faith. You have to read it. Even if you've read it a hundred times, you need to read it again.
Try this: Close your eyes and see yourself slicing a lemon. Now stick that lemon slice between your teeth and when I say, "Three," bite down on it so hard that the juice squirts into your mouth. One. Two. Three. Bite!