A father warns his son not to swim in an alligator lake. The son disobeys, gets attacked, and the father dies saving him. The parable shows why knowing the cost of Jesus' sacrifice should stop you from sinning again.
Does that mean I can do whatever I want and I'm forgiven?
It would be like a boy who goes out camping with his father. They set up camp on the shore of the beach and dad says, son, whatever you do, I'm gonna take a nap. Don't go into that boat because it's alligator-infested water. Kid says, okay, Dad. Dad falls asleep. The kid starts looking at the paddle boat and he thinks, I think I'm gonna give it a go. He goes out into the middle of the lake. All of a sudden, a bunch of alligators start swirling around. He gets a little panicked, tips over, and passes out. The next thing you know, he wakes up with his head on the sand. He turns and looks over and his dad has been clearly mauled by alligators. And he immediately knows, wow, I blew it, and my dad jumped in to rescue me. He saved me from that. Now imagine if that young man then said, thanks, Dad, and then he went back out in the boat and did it again. You would say he doesn't esteem the sacrifice of his father. When you understand that Jesus actually died for you in a very nasty, humiliating way, you don't want to sin anymore.