God: "I looked for someone to take a stand for me, and stand in the gap" (Ezekiel 22:30)
Put simply, faith is believing in something you haven't seen. If you're a Christian, that means believing that what God has said is true and then acting in accordance with that conviction, regardless of what everyone else believes and how the world expects you to act. It means you'll probably act in ways that defy reason. It may mean giving up your ambition, and it may cost you your comfort. It may even cost you your life.
I still find each day too short for all the thoughts I want to think, all the walks I want to take, all the books I want to read, all the friends I want to see. Our time is too short for pettiness, angry words, wounded feelings, crushed souls. Perhaps the measure of life is not in its length, but in its love (John Burroughs).