"If you have faith as a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you." Matthew 17:20
This verse follows an account of the disciples' failure to heal a boy's epilepsy. They had accomplished great miracles before, but this time, they humiliated themselves. What was the difference? Their faith was in themselves, in their past success, in their worthiness to be God's agents, in their own faith. And they failed.
At first glance. this is a pretty discouraging verse. I can't move mountains, so my faith must be microscopic, right?
That's missing the point. It's about quality, not quantity. Even the littlest amount of faith can accomplish great things because of GOD, in whom that faith rests. Worrying about the amount of faith I have puts the focus on me. Then 'faith' becomes a system for trying to manipulate God into doing what I want. (If I just have more faith, God will…) God doesn't have to do what I want and He's already promised to do what I need.
My faith never moves mountains. GOD moves them.