|Zac Poonen gives a wonderful illustration of faith in a sermon called A Life of Faith . In this sermon he gives the example of a man crossing a stream using two bridges - the first is made of concrete, the second is a rickety old tree.
As the man crosses the concrete bridge, no one marvels at his profound faith - since it is plain that the bridge will hold his weight. But the same man has no faith in the rickety tree bridge. The point is that the faith is not an inherant quality of the man - for, were that the case, the same man could traverse both bridges with equal surety. The point therefore is that the concrete bridge engenders profound faith, while the rickety old tree does not.
That is why the we are told to look, not to our own faith, but to the Author and Finisher of our faith - to Christ our Lord who is worthy of faith.
Concentrating on our own ability to generate faith - as though faith were some personal quality, is missing the point. We must look to Christ - and be convinced that God is worthy of the faith we place in Him - that is, that He is able to do abundantly above all that we can ask or think - that He really 'is', and that He is a rewarder of those who diligently seek Him.
Even the faith of a mustard seed is sufficient to send a mountain into the sea.