Jesus is in the business of using messed up people who make a mess.
The story of Jonah is the story of a loving God who chases down his people, even to the depths of the sea. But it's also a story about a guy who makes a mess of things.
Imagine if you were one of those sailors on the ship headed to Tarshish, and a great storm was hammering down on your vessel, so that you thought you were going to die. You discover that the guy sleeping below the ship is the cause of this great storm, and you demand to know what he did to deserve this divinely-inspired death sentence. He tells them, they toss him over the side, storm subsides.
Except, it doesn't really subside for the Sailors. The actual storm subsides, and the waters become still, and they take a moment to catch their breath and thank the Lord of the Universe for sparing their lives. And then they remember that they have just thrown everything of value on the ship over the side of the boat and it was now lost in the sea, along with the guy responsible. Their lives were spared, but their livelihoods may not have been. Someone was going to have to tell the ship owner the story, and explain why all of the goods that he had purchased to sell in Tarshish were now at the bottom of the Mediterranean. I'm guessing they cast lots again to figure out who that assignment was going to fall to.
Jonah even makes a mess of things for the fish. Miraculous nature of the story aside, at some point, the fish vomits. Jonah sees that God's hand was in this, that God whispered to the fish, that the fish listened, that the fish was obedient, and he's right, in the sense that God had ordained that this fish swallow Jonah and that this fish was going to vomit Jonah out on to dry land. Maybe the fish understood all that. Or, maybe the fish just felt like he had indigestion for three days and finally found relief when he vomited this foreign object out onto the shore. (Interesting side note, scientists have speculated on why whales beach themselves, and many of the reasons are due to either sickness or inhospitable waters. Indigestion would fall well within many of the categories!)
Now Jonah has washed up on the shore and God re-engages him with the same assignment he had given him before: I want you to go to Ninevah. And Jonah, apparently freshly regurgitated, decides to obey.
What's interesting about the story of Jonah is that his mess may actually be the very thing that gives him credibility in the city of Ninevah. The city of Nineveh was known for worshiping a fish God named Dagon. Dagon is often represented as some combination of man and fish. If anyone had seen Jonah's ejection from the belly of the fish, washing up on the shore, his message of God's anger towards them would have been received–and quickly!
There is some evidence from a Babylonian historian that something like this actually happened. A historical record dated several hundred years later than Jonah's story talks about a man named Oannas who washed up on the shore and gave divine knowledge to men. Oannas is an alternative spelling of Jonah.
For a more detailed analysis of this, check out this link.
The point is, God uses Jonah's mess for his purposes. That was true for Jonah, and it's true for us He often uses things in our life that we think are blemishes as the very thing that gives our message of his Grace credibility. By the time Jonah finally went to Ninevah, he had nothing of his own effort left to point to. All he had done is make a mess–but it was God who was using it for his purposes.