Finally, my bretheren, be strong in the Lord, and in the power of his might (Ephesians 6:10).
Don't try to fight life's battles in your own strength. When David slung that rock he didn't sling it in his own strength, but in God's. And the victory over Goliath started in his mouth.
34. And David said unto Saul, Thy servant kept his fathers sheep, and there came a lion, and a bear, and took a lamb out of the flock.
35. And I went out after him and smote him, and delivered it out of his mouth: and when he arose against me, I caught him by his beard, and smote him, and slew him.
36. Thy servant slew both the lion and the bear: and this uncircumcised Philistine shall be as one of them, seeing he hath defiled the armies of the living God.
37. David said moreover, The Lord that delivered me out of the paw of the lion, and out of the paw of the bear, he will deliver me out of the hand of this Philistine. And Saul said unto David, Go, and the Lord be with thee.
And in God's strength he defeated the bear, lion, and the Philistine. But notice in all 3 battles he went after them. Maybe the devil has stolen some things from you, well you need to go after him in God's might and recover it. You are more than a conqueror because I don't have to fight in my strength, but in God's might. You're not fighting to win, Jesus did that for you (Colossians 2:15). Your fight is to maintain the victory Jesus has accomplished. It's never about your strength, but his might.
And he said unto me, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me.
Therefore I take pleasure in infirmities, in reproaches, in necessities, in persecutions, in distresses for Christ sake: for when I am weak then am I strong.