Among the old testament prophets, Jonah is the one with whom one can relate to most easily. He is a common man, called upon by Yahweh for a particular purpose. Initially reluctant and lazy but then relents. However, the very fact that Yahweh calls him does not 'purify' him of his human inclinations. He carries with him his basic human qualities right to the end.
After the episode at sea and having spent three days in the belly of the fish, he decides to go to Nineveh and tell the people there God's message, not out of fear or conviction but more out of guilt. Once his job is done he expects to see the fulfilment of God's prophecy. Not seeing God send out his wrath, he feels dishonoured and his work disrespected. He sulks. His self-centredness (not selfishness) prevents him from seeing the larger picture unfold.
In and through the ups and downs of Jonah it is easy to miss one of the central messages of the narration: God changes! The only difference between God changing his mind and heart and Jonah's change is that the change is brought about for the good of the other. God relents from sending down his wrath on the people of Nineveh because he sees them repent and take responsibility for their lives. Jonah fails to see the struggle of Nineveh because his focus energy is all trained on his own work and struggle.