Psalm 27:13-14 King James Version (KJV)
13 I had fainted, unless I had believed to see the goodness of the Lord in the land of the living.
14 Wait on the Lord: be of good courage, and he shall strengthen thine heart: wait, I say, on the Lord.
Depression is a type of fainting that is common in life. It is a mental fault, and an emotional response to feeling overwhelmed, overcome, "fenced in", "backed into a corner", being misunderstood, rejected, lonely, "out of sorts", and a host of other emotions. It is crucial for the believer in Jesus Christ to learn how to recognize the attack of the enemy.