The Eagle, the Jackdaw, and the Shepherd explained simply

One day a Jackdaw saw an Eagle swoop down on a lamb and carry it off in its talons. "My word," said the Jackdaw, "I'll do that myself." So it flew high up into the air, and then came shooting down with a great whirring of wings on to the back of a big ram. It had no sooner alighted than its claws got caught fast in the wool, and nothing it could do was of any use: there it stuck, flapping away, and only making things worse instead of better. By and by up came the Shepherd. "Oho," he said, "so that's what you'd be doing, is it?" And he took the Jackdaw, and clipped its wings and carried it home to his children. It looked so odd that they didn't know what to make of it. "What sort of bird is it, father?" they asked. "It's a Jackdaw," he replied, "and nothing but a Jackdaw: but it wants to be taken for an Eagle." If you attempt what is beyond your power, your trouble will be wasted and you court not only misfortune but ridicule.