Strive to ride a specific single track in as few gears as possible, I am always aiming for ONE.
,
,
If you:
Pedal hard down hill, you can often coast up, saving a ton of energy.

If you:
Coast down hill, you will often pedal up, hard once near the top burning a large amount of energy.

If you:
Use your brakes going down hill you will often be walking up hill dragging the bike using an ETREME amount of energy.
And you will damage the trail....