"Now Faith, in the sense in which I am here using the word, is the art of holding on to things your reason has once accepted, in spite of your changing moods. For moods will change, whatever view your reason takes. I know that by experience. Now that I am a Christian I do have moods in which the whole thing looks very improbable: but when I was an atheist I had moods in which Christianity looked terribly probable. This rebellion of your moods against your real self is going to come anyway. That is why Faith is such a necessary virtue: unless you teach your moods 'where to get off', you can never be either a sound Christian or even a sound atheist, but just a creature dithering to and fro, with its beliefs really dependent on the weather and the state of its digestion. Consequently one must train the habit of Faith." Mere Christianity
Many years ago, when I was a young Christian, I remember seeing the graphic illustration above of what C. S. Lewis has, here, so eloquently put into words. FACT is the engine of the train of the Christian life which pulls the car of FAITH behind with the caboose pulling up the rear, filled with FEELINGS.
There are many debates today about what exactly are the historical facts which can be known for certain as true about the foundation of Christianity. As much as that topic is debated it hasn't changed the evidence we have for early Christianity; we have that evidence in the New Testament. There is an objective reality on which my faith is based. That reality was what it was long before I was born. It will be what it will be long after I am gone from this planet as we know it now.
In a world that is in a constant state of flux it is good to know there are some things which never change. In some ways I know more today than I did at thirteen years of age about the historical foundation of Christianity; in some ways I know more about the FACT engine of the Christian train. But in some ways I know less than I thought I knew when I was thirteen. Be that as it may, the Gospel of Jesus Christ is unchanging, regardless of my faith or my feelings or even my knowledge about it. That Gospel is the engine which pulls my little life along, even when my faith is minuscule and my feelings constantly want to jump the track in one direction or another.
"Jesus Christ is the same yesterday and today and forever." Hebrews 13:8