Summary: What kind of strength are you getting from your personal devotions?
1 Sam 17:34-37
34 And David said unto Saul, Thy servant kept his father's 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 defied 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. KJV
David had great opportunities to spend time alone with God in the fields with the flocks. Because of this time alone he got to mediate on God's glory and greatness as revealed in His creation works both heavenly and earthly. This is where the seeds of so many of the great Psalms were planted in his heart while the daily meditation watered them so that when it came to facing a giant David had already faced some things that were bigger than him.
A lion and a bear are no easy animals to fight and win yet God gave him the victory over both with just a sling and bare hands. A large human was no major feat for the animals only acted out according to their nature and did not defy God or defame His people. Goliath had done both so it was an easy thing to believe that if God protected him from fierce animals a fierce human would go down as well. Faith nurtured in daily solitude handles adversity well for it knows the omnipotent One. What animals and giants are you facing that would be easily defeated if you spent more time alone with Him?