Murmuring

To murmur is to give Satan some of your agency power. That power (and time, since power = work/time) is wasted. If you're not working toward a righteous desire your work=0, so power=0

It could have been combined with God's grace and priesthood power to help you achieve your righteous desires.

"The same amount of work is done when carrying a load up a flight of stairs, regardless of speed. But more power is needed when the work is done in a shorter amount of time."

When you align your will (and power) with His, He will add his power to yours, enough to accomplish His miracles (the part that He adds is "grace").