Take your time, find a place with a steep Terrain where you feel comfortable. Practice slow and calm descents, recognize the point where the traction ends. Repeat, until you understand how the bike behave and what is the maximum braking force you can apply without loosing Control. 

Once you know that, include additional features. Find a steep and traversing slope and repeat the process. Then include surface obstacles like roots and rocks and practice again. You are ready. Go to the trail you are scarred the most. Face it with confidence, not recklessness.

Once you overcome the great wall quarry you are ready to challenge Mr. Lunch.