To the degree that the believer insists that their belief in the divine is on the same level as or even stronger than their belief in the solidity of the surface on which they stand, they are basically engaging in self hypnosis to willfully install and elevate a belief which cannot earn its place in the usual manner. They are deliberately deluding themselves.
On the other hand, a believer who recognizes they have insufficient means to convince an intelligent, fair minded third person but chooses to believe anyway for reasons they can articulate is certainly not delusional.
On the other hand, a believer who recognizes they have insufficient means to convince an intelligent, fair minded third person but chooses to believe anyway for reasons they can articulate is certainly not delusional.