The great commandment to love God with all of our heart is rooted in monotheism.  That is, all other gods are false, and there is no other god for whom we need to reserve some love, service or sacrifice.  Sometimes it takes gut wrenching ruthlessness with our own heart to set aside competing loves.  The failure to love God with all of our heart always reveals some lurking idol that needs to be cast out.  Do it for the love of the One!

“Hear, O Israel! The LORD is our God, the LORD is one!  You shall love the LORD your God with all your heart and with all your soul and with all your might.” Deuteronomy 6:4-5 (NASB)