"If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you." What are we to make of this passage? Is Jesus exaggerating a bit, or is what He says literally true? Indeed, it does sound rather like the "magical thinking" characteristic of childhood: if we believe something strongly enough, it will surely happen.
As we mature into adulthood, however, we learn very soon that no matter how strongly we desire something and how firm our belief that it will happen, things seldom work out in our lives according to our expectations.
Obviously Jesus isn't say that if only we believe something strongly enough, it will happen. True Christian faith isn't simply a matter of believing, or "claiming the promise," according to certain "possibility" cults. Faith is the product of our relationship with the living God.
Genuine faith presupposes that we are living our lives (or at least striving to) in communion with the triune God, aligning our personal desires with His perfect will, so that in the end we "cease to exist" as self centered individuals, saying with St. Paul, "It is no longer I who live, but Christ liveth in me."
Unfortunately, we too often behave like little children in the thralls of magical thinking, wanting what we want because we think we want it....but if truth be told, we seldom really know what we want. As the saying goes, Be careful what you wish for...you may get it.
If our faith in God is genuine, we will never consider that He bend His perfect will to our own self-centered desires. Rather, we must cast aside our egocentric thoughts and desires, affirming with the Theotokos, " "Let it be unto me according to Thy word." Only then can our faith work miracles: when that which we desire conforms to the perfect will of God.