Once upon a time there was a Shepard with 100 sheep.
Then one of his sheep went missing.
The Sheppard went looking for his sheep.
The Shepard found the sheep safe.
The Shepard was happy to find his sheep, he brought him back home and all was well.
The sheep represent Gods followers, and the Shepard represents God. The Shepard had to find the sheep and bring it home, he doesn't punish it because he is happy that the sheep is safe. God does the same by helping sinners get back on track.