Both David and Saul receive human intel, but where David inquires, Saul imagines. God reveals to David, “I will give the Philistines into your hand” (v. 4). Saul imagines, declaring, “God has given [David] into my hand” (v. 7). As the Philistines were delivered into David’s hand, so Saul believes David is delivered into his hand.
David hears God’s word. Saul puts words into God’s mouth. David inquires of Yahweh. Saul imagines Yahweh. Matthew Poole writes, “He easily believed what he greedily desired, though his own experience had oft showed him how strangely God had delivered him out of his hands, and what a singular care God had over him.”

Your imagination is a dangerous way to read the facts and discern God’s will. But this is not only how many seek guidance, it is how they do theology. When you receive intel, inquire, don’t imagine. How do you inquire? Prayerfully read God’s Word. This assumes the indwelling and illumination of the Holy Spirit.
This is how delusional sinful man is in the darkness of his depravity—he presumes God is with him, when God has proclaimed that He is against Him. “The wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth” (Romans 1:18). God tells man he is condemned. Man replies, “You’re so sweet. I know you love me.” God is patient and long-suffering, but we are children of wrath. Yes, grace is offered, but it is offered precisely because we stand under God’s curse. Those condemned in Adam should not behave as though they were an angel of heaven.
Saul is told and and Saul imagines. David knows, yet David inquires (v. 9). David doesn’t act on human intel alone. He doesn’t act on human intel supremely, which is to say, David doesn’t rely on his own intelligence. David models for us what it means to “Trust in the LORD with all your heart.” Saul however, “lean[s] on [his] own understanding” (Proverbs 3:5).
David is absolutely unique. He is the Lord’s anointed. He is God’s king. He has a prophet. He has a priest. But you have the Word of God, the revelation of the Son of David, and the Spirit of Christ to illuminate the Word He inspired. You won’t receive such specific guidance, but that’s not really what you need. You need Biblical wisdom and truth. If you can exclaim with the psalmist, “Oh how I love your law! It is my meditation all the day” then you may also rejoice declaring, “Your commandment makes me wiser than my enemies, for it is ever with me. I have more understanding than all my teachers, for your testimonies are my meditation. I understand more than the aged, for I keep your precepts” (Psalm 119:97–100). This doesn’t mean that you walk with your head up as though you can see what others do not. It means you walk in humility and obedience, trusting your God.