I am currently reading: Gospel Treason: Betraying the Gospel With Hidden Idols by Brad Bigney.
In Chapter 4, in a section titled "Our Hearts Need Regular Alignment", the author says this:
"The heart is a tricky, slippery little creature that most often flies under the radar, giving us no reason to think about it. We live day after day, oblivous to the idols that are running up and down the aisles of our hearts, darting in and out of the clothes racks of our thoughts like wild hooligan children running loose in Walmart while their mother shops. And when we hear the occasional thuds that echo up from the recesses of our hearts, we tend to blame them on whatever or whoever is around us, until darkness or conflict sets in. And that's because we don't really see what's in our hearts until God takes us through some dark time, through some harsh trial that develops and exposes what was in our hearts all along.