Faith is known as Shraddha. If you read Prashnouponishad, you will realize that faith is the second step in creation. In its core, faith is the soul is immortal. You may know it. But yet, the long standing attachment to body , we constantly are afraid. We believe in heaven and hell. But in that case the body dies there is something else that lives and God to heaven or hell.
So to really understand faith you have to reach the soul.
The most powerful statement I have is in the Bible
And He *said to them, “Because of the littleness of your faith; for truly I say to you, if you have faith the size of a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible to you
Yet with the slightest bit of hardship we falter. Forget parting the Red Sea or moving mountains, we worry about was that sneeze cancer? And how much faith do we need? Mustard seed – minuscule.
So how can we grow in faith? I want to move mountains!!! yeah sure! I was making fun. But all great miracles came from faith. Why are some people better than others in faith ? How can I change ?
Answer is slowly. There are certain secret mediation techniques that speed it up. But here is an excellent guideline from Paramhansa Yogananda
There is a way to cultivate belief until it becomes faith or absolute conviction. Belief is the initial recipient attitude of the mind necessary or planting the seed of a hoped-for outcome. As a successtul farmer earns the laws of planting for a good harvest, so a truth-seeking individual must learn how to cultivate the soil of belief so that it may yield the desired result. When the seed of his aspiration is continuously watered with belief in the Self and in the intercession of a master-as when the disciples appealed to Jesus—it sprouts into faith that the desired result will inevitably be accomplished.
~ Sri Paramahansa Yogananda,
899, The second coming of Christ.