Okay, the first part of this verse means to fear God, to keep God number one in your life, to keep HIm God in your life.
What I want to talk about is the second part of the verse. When we notice our hearts have gotten hard (or are on their way to getting hard, losing tenderness) we are going to deceive ourselves and we're going to fall into a mess (at least internally).
God's heart is never hard. Never. And God has seen it all.
If we find ourselves callous and without compassion toward ANYONE, we need to immediately as God to change our hearts.
I've caught myself with a hard heart at times. And it is ugly. In these ugly moments I might hear someone get real emotionally concerned about someone having a seizure. For 12 years I've watched my middle son have several seizures a day. Seizures are no big deal for us anymore. BUT, this doesn't mean I turn my compassion off toward others who might experience this. I remember the first time I saw someone have a seizure -- it is very scary. And if I catch myself getting callous I need to remember that moment, how I felt when I watched a friend lose all control and be taken control by something other than herself.
Is there something you've grown callous about? Something that is everyday for you but not for others? Don't grow hard. Remember what it was like before it was typical for you. Have compassion. Show compassion.