What is Faith?

I've been reading Mere Christianity (CS Lewis) slowly ... paragraph by paragraph sometimes... in the mornings. Recently it's led me on a journey into what faith is, the different types of faith, what it means to live by faith, etc. Part of it relates to what I've already been learning about humility and being "poor in spirit." In this particular chapter Lewis talks about coming to the point where we realize we've done our utmost and are still incapable of attaining righteousness. This is the point at which we need to say, to God, "I can't, you need to do this for me." That is, we need to give up. He then continues to explain that this means leaving all our trust in God; trust that He will cause things to turn out all right in the end. I think my favourite quotation from this section is as follows: 

There would be no sense in saying you trusted a person if you would not take his advice. Thus if you have really handed yourself over to Him, it must follow that you are trying to obey Him. But trying in a new way, a less worried way. Not doing these things in order to be saved, but because He has begun to save you already. Not hoping to get to Heaven as a reward for your actions, but inevitably wanting to act in a certain way because a first gleam of Heaven is already inside you.

I found that a very apt summary of the ragtag thoughts & feelings I've been pondering over the last while. I love finding succinct quotations of something that I've already been learning and discovering... it's very encouraging.