The Power of the Spirit
You've heard of 5 Hour Energy drink, or Red Bull? These boost the body, but how about your soul. For that you need the Power of the Spirit of God.
So Samuel took the horn of oil and anointed him in the presence of his brothers, and from that day on the Spirit of the LORD came upon David in power . Samuel then went to Ramah . 14 Now the Spirit of the LORD had departed from Saul, and an evil spirit from the LORD tormented him. 1 Samuel 16:13-14
Notice the contrast. David now had power because the Spirit of God was upon him. Saul's disobedience and pride led to God taking away the Spirit from him and thus he was left vulnerable to greater demonic influence and bouts with depression.
In the power of God's Spirit, David went on to kill lions, bears, Philistines, and giant Philistines. He lead Israel to become a powerful kingdom and groomed his son to lead an empire.
Through humility, surrender, and obedience we can access the power of the Spirit God has placed in us.