Preparation of the mind to do something can be trying. But once you get it in your mind you seem to move in the direction momentum takes you. You seem to be running on adrenaline. It is when that momentum and adrenaline stops you have that quivering moment. That moment that can make you cry. That moment that makes you paralysed with fright. That moment of doubt. Look how it ended in this passage.
Immediately Jesus made the disciples get into the boat and go on ahead of him to the other side, while he dismissed the crowd. After he had dismissed them, he went up on a mountainside by himself to pray. Later that night, he was there alone, and the boat was already a considerable distance from land, buffeted by the waves because the wind was against it.
Shortly before dawn Jesus went out to them, walking on the lake. When the disciples saw him walking on the lake, they were terrified. “It’s a ghost,” they said, and cried out in fear.
But Jesus immediately said to them: “Take courage! It is I. Don’t be afraid.”
“Lord, if it’s you,” Peter replied, “tell me to come to you on the water.”
“Come,” he said.
Then Peter got down out of the boat, walked on the water and came toward Jesus. But when he saw the wind, he was afraid and, beginning to sink, cried out, “Lord, save me!”
Immediately Jesus reached out his hand and caught him. “You of little faith,” he said, “why did you doubt?”
And when they climbed into the boat, the wind died down. Faith is the size of a mustard seed. You must understand it is human to be frightened but like toning for a marathon, the more we practice the better it will be. Faith will be second nature.