Self.
Faith will never be weak if self be weak, but when self is strong, faith cannot be strong; for "self" is very much like what the gardener calls the "sucker," at the bottom of the tree, which never bears fruit, but only draws away the nourishment from the tree itself. Now, self is that sucker which diverts the nourishment from faith, and you must cut it up, or else your faith will always be "little faith," and you will have difficulty in maintaining any comfort in your soul.
Strength through Joy.
It is when the mind is happy that it can be laborious. "The joy of the Lord is your strength."
The Refiner's Fire.
There is not an ingot of silver in heaven's treasury, which has not been in the furnace on earth, and been purified seven times; there is not a gem which the Divine Jeweller has not exposed to every sort of test; there is not an atom of gold in the Redeemer's crown which has not been molten among the hottest coals, so as to rid it of its alloy. It is universal to every child of God. If you are a servant of the Lord, you must be tried "as gold is tried."