What is it that you are trusting in? A lot of people have faith, but if that faith is in the wrong thing then that faith has been misplaced. The reason that Peter could make the request that he did, was because Jesus had proven Himself worthy of Peter's trust.
If your faith is in the right thing, then you can make any request knowing that Jesus is more than capable of answering those requests. One of the biggest problems that we have is simply not asking God to work and move on our behalf. We have not often times, because we ask not.
Genuine faith requires action. It is one thing to make a request by faith, but there comes a time that you have to then act in faith. Peter had asked Jesus if he could get out of the boat, now the time had come for him to step over the edge of the boat and get out onto the water.
So we have had all of this teaching on doing things by faith, but what exactly is faith? Some people have this idea that faith is walking off of a cliff and just hoping that God will catch you. But the Bible teaches us that faith is something that is solid and secure.