We must not exercise faith lightly or ask for things that are improper.
10 Remember that without faith you can do nothing; therefore ask in faith. Trifle not with these things; do not ask for that which you ought not.
Elder Bruce R. McConkie wrote:
“Perfect prayers are always answered; proper petitions are always granted. The Lord never rejects a prayer uttered by the power of the Spirit, or denies a petition sought in the name of Christ, that accords with the divine will.”
(A New Witness for the Articles of Faith , 384.)