about whatever you ask
When we read this verse, we might think, in our selfish way of thinking, Christ is offering us some kind of blank check to grab anything we want. However, there is in this verse the word "believe." Belief is our path to God. Without belief, our path leads to Satan. We do have in Christ’s truth about the concept of belief, indeed, a form of a blank check. Belief is an action of the heart, mind, and soul. Where and how we point our belief is of utmost importance. What do we ask for in prayer? Do we ask for all the selfish things and "stuff" we want or do we surrender up ourselves in unselfishness? If we ask for selfish things we may receive them but we will not want them after we have them.
If we ask for unselfish things by not even asking for anything for ourselves but only for others, we will not have anything for ourselves, except the mighty blessings of God. For this verse is not so much about getting what you want. The verse is about the doubt in your heart. When the doubt in your heart is gone, when there is not a shred of a question about what God wants from you, there is left in your heart no request for anything for yourself. When all the doubt in your heart is gone so is all the selfish pride, all the selfish ambition, and all the selfish making of lists of what you might want God to provide. And that issue of moving the mountain? When your pride is gone, the mountain can stay where it is because you find God did not want it moved anyway, and when you find out God did not want the mountain moved, the mountain disappears.