So said Saul to David, just before the shepherd boy cut off Goliath’s head in single combat.
Boy, nobody believed in David. Not his brother. Not his king. I guess Saul figure there would be nothing lost if David lost: You are not able. — 1 Sam.17:35
And then David went out and, with a stone and sling, showed he was able.
Of course, God was behind the miracle. The story of how David sunk a stone in the giant’s forehead is actually the first laser-guided projectile. Yeah, God was the laser guidance system.
And the giant fell down. And David ran to him, took his own sword and cut his head off.
The Philistines, who no doubt were thinking David wasn’t able, panicked and ran.
The next time someone tells you you’re not able, laugh and go out and do it in the power of God.