Some years ago I remember hearing a pastor and thinking he sounded hollow, or that something just didn't seem right, or at least that in spite of the way he preached which was an emulation or model of "good preaching", and that there was good in his message, I frankly was glad when it was over. Later it came to light that he was having an emotional affair with a woman from another city. I don't know if I had just been having a bad day or had been given a measure of some kind of discernment. But there are few issues I'm more concerned about than losing my heart in God, really none.
This doesn't have to be in reference to an adulterous affair. It could involve any number of things that move us away from God. Paul warns about the danger of wanting to get rich and that by so doing some had wandered from the faith and pierced themselves with many sorrows.
A good Biblical case in point is David. A man, no less, after God's own heart. And yet a man who was losing his heart in God through his adultery and then murder (arrangement of the death) of the woman's husband. David ends up being miserable and from this escapade we have one of the greatest psalms to meditate on and work into our hearts and lives.
When I'm losing my heart in God I no longer feel quite at home in God. My heart is elsewhere. Isn't that idolatry? I find that in the recognition, acknowledgement and confession in turning back in penitence to God I begin to find my heart again in God, though this is an ongoing project for me to both guard and deepen. And I do fail at times but then can get back on track, and I've learned to endeavor to do so as soon as I realize what's going on (which probably means not very soon, like my annual factory hearing tests where for some time I don't recognize the small beep sounding in my ear).
We're to guard our hearts and by our heart, seek God's face. Is it better to have our own way or live our own life not at home in God in our hearts? Or is it better to struggle in any number of ways and really be at home in God in our hearts, even if oftentimes the signal seems weak?