Isaiah 55v8-9 “For my thoughts are not your thoughts, neither are your ways my ways, declares the LORD. For as the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts.”
Deuteronomy 4v16-18 “Beware lest you act corruptly by making a carved image for yourselves, in the form of any figure, the likeness of male or female, the likeness of any animal that is on the earth, the likeness of any winged bird that flies in the air, the likeness of anything that creeps on the ground, the likeness of any fish that is in the water under the earth.”
Idolatry is loving/worshipping/serving any good/bad thing that is not God. To identify your idol, just consider the thing(s) that you think about late at night; honestly reflect on what/whom the true affections of your heart are dedicated to. It is also possible to think we have come to know God, but to instead be worshipping a god of our own or another’s imagination. One current fast selling book, The Shack, presents an idolatrous image of God in the likeness of male and female people. This book is inspiring thousands of people to worship a god of an author’s creation who is so far from being anything like God who has revealed Himself to us through the bible alone. We normally arrive in a place of ‘kind-of-like-God’ idolatry if we have a low view of scripture and say things like “To me, god is…”. No, God is not someone you are free to invent to suit yourself, He must be taken as He has revealed himself to be. I hope that you can get a handle on this extract from J.I. Packer’s Knowing God:
God is not the sort of person that we are; His wisdom, His aims, His scale of values, His mode of procedure, differ so vastly from our own that we cannot possibly guess our way to them by intuition or infer them by analogy from our own notions of ideal manhood. We cannot know Him unless He speaks and tells us about Himself. But in fact He has spoken. He has spoken to and through His prophets and apostles, and He has spoken in the words and deeds of His own Son. Through this revelation, which is made available to us in Holy Scripture, we may form a true notion of God; without it we never can. Thus it appears that the positive force of the second commandment is that it compels us to take our thoughts of God from His own holy Word, and from no other source whatsoever.
That this is the commandment’s positive thrust seems plain from the very form in which it is stated. Having forbidden the making and worshipping of images, God declares Himself ‘jealous’ to punish, not image-worshippers as such, but all who ‘hate’ Him, in the sense of disregarding His commandments as a whole. The natural and expected thing in the context would be a specific threat to image-users; why, instead, is God’s threat generalised? Surely this is in order to make us realise that those who make images and use them in worship, and thus inevitably take their theology from them, will in fact tend to neglect God’s revealed will at every point. The mind that takes up with images is a mind that has not yet learned to love and attend to God’s Word. Those who look to man-made images, material or mental, to lead them to God are not likely to take any part of His revelation as seriously as they should.
Packer (1973) Knowing God, Hodder and Stoughton, p49.
The Shack is not just idolatry, there are a lot of other issues with the book. I recommended a review by Tim Challis if you want to look further into it.