We can define “desire” as one of two main ways, as “feelings / emotions,” or as “a want or wishful hope.”
Both of these definitions have the same non-relevance in regards desire being non-intellectual and having no necessary connection to faith, or no necessary connection to receiving the promise.
Faith is simply a mental assent to God’s truth. Having a desire or wishful hope to be saved, and mentally assenting to the gospel propositions as truth, is not the same thing.
The bible does speak of a “sound mind” and that we are to renew our minds. This is in two ways. The first and foundational meaning is to know the propositions of Scripture and assent to them, and deductively apply them to yourself and to decisions of good and evil about reality. You remove false propositions and replace them with true propositions from Scripture, and you remove invalid reasoning with deductive reasoning. The second part is what we call the psychological state of the mind. A renewed/mature mind will experience a more stable state of joy, and without even trying will keep gravitating towards wanting or desiring to please God rather than the self or man. However, as John says in 1st John 3, our hearts or that is, our irrational emotions and thoughts can condemn us, even when it is not true. Thus, you never base what is true or false by your emotions or by your up and down desires. You base what is true on “faith.” You do not base truth by sight for sensations is no truth or produces truth. Or simply put because we live by faith alone, and since sight is not faith, we do not live by sight. By the same reasoning, we do not live by feelings and desires, because these not faith. To go from sight to a proposition is invalid; however, it is just as invalid to go from desire/feelings to a proposition. In both case one is making a category error and denying the law of identity.
A wishful hope for healing is not faith. A wishful hope is not a mental assent to the fact that in Christ’s atonement “you” are already healed (Isaiah 53); that is faith. To desire to be healed, is on one hand something Jesus presupposes that people want; however, because desire to be healed is a command then even if you do not “feel” the desire to be healed, you can be obedient, if by nothing else, by pragmatically seeking to be healed by faith, in how the bible says to grow faith.
The desire would and often should be there, but it is not faith, and it is not needed to obey God’s commands. We should desire and seek for a sound mind, both in the intellectual, spiritual aspect, and also for a constant state of joy and desire for God. However, we do not start off with a mature mind when we are born again. We renew our minds by the means God has given us. If we do not start off with a perfect state of mind when born again, and having such a mind is required for us to ask and obtain our requests from God, then it would never happen. Think about the examples of faith in the Bible? Samson, when his eyes were stabbed out and bound in chains of slavery, was his mind in perfect joy? All he did was believe God would be faithful to His promise to use Samson. His faith was so great he is mentioned in Hebrews 11 with David, Moses and Abraham as a man who the world was not worthy to have utter Samsons’ name on their filthy lips. It is true that having a joyful and peaceful state of mind for good things is able to help, so that even prophets asked for music to be played, and David would retreat and quietly meditate on God’s goodness; however, with or without the perfect desire, only one thing is needed, a mental assent that God will do what He said, without doubting it. When this is done you can ask for 100 mountains to throw themselves into planet Saturn and it will happen.
Also, like assenting to the fact that bananas are your favorite fruit, it is either mental assent that you do, or if they are not and you still affirm, “bananas are my favorite fruit,” you mentally assented to a lie or a delusion. A mental assent does not merely mean you affirm something like (2 plus 2 equals 4), if the context demands it. It is one thing to assent that figs exist, and a different thing to assent that figs are “my” favorite snack. This is either true or false; if false and you say it in your mind anyway, then all you have done is indulged in a mental delusion.
When we realize our faith is not where it should be we are told to renew our minds. We take off the old falsehoods and replace them with the truth. We “confess” them, even when we know we have doubts, not because we are delusional, but because the promise of God is that we can renew our minds and that the Spirit will help to strengthen us. We confess God’s promises, knowing God will be faithful to sanctify our minds so that soon, we can assent to them without doubts. Because the “foundation” is not us, but GOD, we have the confidence to read God’s promises, and confess them knowing God will renew and strengthen us, so that soon the doubts will be gone and an indomitable faith remains.