When we think of Jonah, we don't often think of idolatry. We think of this scared little dude who was told to go prophesy to Nineveh, but he didn't want to get beat up, so he ran the other way and got swallowed by a whale where he learned his lesson and obeyed God. Where does idolatry fit into this? He wasn't making carved idols. He wasn't bowing down before a lifeless image. All he did was run away from God.
And that's what idolatry is. It doesn't always require a carved, drawn, or even imagined image. The only thing idolatry requires is obedience to something that is contrary to God. See, one of the ways we worship God is to obey His commands. God says "thou shalt", and we shall. God says "thou shalt not", and we shall not. But what about when God says "thou shalt", and we do not, or when He says "thou shalt not", but we do? In this case, are we not giving our obedience, which is rightfully due to God, to something else?
And this can be anything. Even, as is the case with Jonah, our own selves. Jonah disobeyed God in favour of his own fears. But God is not one to just let disobedience slide. Jonah disobeyed, and as a result, he found himself being swallowed by a whale, and the text suggests he may actually have died and spent some time in Sheol. Jonah suffered so his idols may be revealed, and that he would turn from them.
God does not operate a karma system in this life. Good works do not necessarily bring good things, neither do bad works necessarily bring bad things. But there is a general principle that our idols will cause us to suffer. The chances of us being swallowed by a whale are particularly slim, but think of all the things in your life that you base your happiness on. Could you lose them? Most likely. But here's the question: Could you survive without them? The obvious answer is yes. Absolutely yes, you could live without the perishable things you love so dearly. Why? Because God Himself is enough. Let us not give Him motivation to prove it. Let us worship Him alone, not worshipping these other things, but rather let us use these things, assuming they are not idols in and of themselves, to worship Him.