Jesus often mentions that it is faith that heals, rather than his word or touch. (Faith=pistis in the original Greek, same term that is translated as "belief" at other times)
In this story, Mark 9:14-29, a father who seeks healing for his son cries out in anguish, "I believe; help with my lack of belief!"
That is a strange sentence. In the space of its mid-sentence semicolon, the man goes from belief to unbelief to a request for help with the unbelief.
But the mind does move that fast, and faith gained in a nanosecond is lost even faster. The father here has the same problem the disciples complain of when they ask, in Luke 17:5, "Increase our faith!"
(By the way, neither the father in Mark 9 nor the the disciples in Luke 17 get any direct response.)
What is the help for that so-quickly lost faith? What would it mean to "increase" faith?
Let's take faith/belief to mean an experienced continuity, at the level of perceptive feeling, with the "heavens" or the spiritual world or the mind of God.
The help the man asks for, the increase the disciples ask for, is that the faith be made steady, 24/7, even eternal. As when, in Thessalonians 5:17, Paul outrageously suggests that we "pray continually."
Maybe this is impossible for the verbal or imagistic mind. But maybe our feeling life can be educated so that it looks continually up. That would be a happy state, predicted in Psalm 1:2 --
His delight is in the law [=teaching] of the LORD; and in his law doth he meditate day and night.
all blessings to all,