Occasionally we will have a patient in the hospital who is on a breathing machine who is on four different pressers to keep their heart beating and they are clinically brain dead. However, when it comes to conveying this reality to the family, some don't accept the reality and say instead, "If we just believe strong enough, God will heal them".
I think this is a misunderstanding of faith. Faith is not the strength of our own will or strength of belief in God giving us what we want or to change Gods mind. Faith is aligning our will with God.
And what does God want? God wants to establish a perfect people and society built upon a foundation of temples and His priesthood authority where He can send his children to family who will raise them up "without sin unto salvation".
When your purposes are aligned with God in this manner, like the Brother of Jared, you can move mountains. I think this is why the Brother of Jared was said to have such great faith. After God had destroyed Babel, Jared and His brother desired to establish a perfect society according to the design and will of God.
Matt 6:25 Therefore I say unto you, Take no thought for your life, what ye shall eat, or what ye shall drink; nor yet for your body, what ye shall put on. Is not the life more than meat, and the body than raiment?
When we pray, we are to pray over our flocks and fields. But, do we spend most of the time concerned with personal temporal matters instead of praying about others and accomplishing God's purposes?