‘And he prayed to YHWH, and said, “I pray you, O YHWH, was not this what I said when I was yet in my own country? Therefore I rushed to flee to Tarshish, for I knew that you are a gracious God, and merciful, slow to anger, and abundant in lovingkindness, and repent yourself of the evil. Therefore now, O YHWH, take, I beg you, my life from me, for it is better for me to die than to live.”
So in his anger Jonah prayed that YHWH would take his life from him because he felt it better to die than to live. That may have been because he felt that he had been discredited as a prophet, or because he could not bear to think of Assyrians as having been forgiven. What is certain is that it was because he regretted having been involved in what had happened. And he pointed out that the reason why he had been in such a hurry to flee to Tarshish was because, being aware of YHWH's propensity for mercy, he had wanted to avoid having anything to do with YHWH's plans.
We should note the reason that Jonah gives for his anger. It was because he had known that if he preached in Nineveh and declared their destruction within forty days, God, with His soft heart, would inevitably spare them thus making a fool of Jonah. And he said that he knew this because God was gracious and merciful slow to anger and abundant in lovingkindness, and so much so that if the Ninevites repented He would change His attitude towards them and be gracious to them.
This then was Jonah's picture of what YHWH basically was, and is one of the points being underlined in the prophecy. That YHWH is merciful to all who call on Him in repentance and faith.