Guarding the heart means paying attention to what’s happening inside your mind and stopping destructive thoughts before they take root. It’s spiritual watchfulness.
The Orthodox tradition calls this nepsis, from a Greek word that means to stay awake, to keep watch, to inspect carefully. Think of it like standing guard at the door of your heart. Every thought that tries to enter gets checked. Does this thought lead me toward God or away from him? Does it build up or tear down? You let the good ones in and turn the bad ones away before they can settle in and make themselves at home.
This isn’t about positive thinking or mental hygiene. It’s spiritual warfare. St. Peter warns us to “be sober, be vigilant, because your adversary the devil walks about like a roaring lion, seeking whom he may devour.” The battleground is your mind. The stakes are your soul.
Why Your Thoughts Matter
The book of Proverbs puts it bluntly: “Above all else, guard your heart, for everything you do flows from it.” The desert fathers took this seriously. They understood that thoughts govern your life. A thought of resentment, left unguarded, becomes a grudge. The grudge becomes bitterness. Bitterness poisons everything. But it started with a single thought you could’ve caught at the door.
St. Hesychios, one of the great teachers on this subject, described watchfulness as “fixing and halting of thought at the entrance to the heart.” You’re not trying to empty your mind or stop thinking. You’re learning to notice what you’re thinking and to judge those thoughts honestly before God.
This takes practice. Years of it, actually. But it’s how the passions get uprooted. It’s how you move from being controlled by anger, lust, envy, despair toward the freedom of dispassion, not feeling nothing, but not being ruled by disordered feelings.
The Jesus Prayer and Watchfulness
The Jesus Prayer is the tool most Orthodox Christians use to develop this watchfulness. “Lord Jesus Christ, Son of God, have mercy on me, a sinner.” You pray it throughout the day. While you’re driving down I-10 to work. While you’re waiting for the coffee to brew. While you’re lying awake at 2 AM because your mind won’t shut up.
The prayer does two things. It focuses your attention on Christ instead of whatever anxious or angry or lustful thought is trying to grab you. And it calls down God’s mercy on the actual battle you’re fighting. Elder Ephraim called the Jesus Prayer an axe that strikes at the root of the passions. But you’ve got to swing it consistently.
When you catch yourself spiraling into worry about money or replaying an argument or fantasizing about something you shouldn’t, that’s the moment. Stop. Pray. “Lord Jesus Christ, have mercy on me.” You’re not suppressing the thought through willpower. You’re replacing it with prayer and asking God to help you see it clearly.
Starting Small
If you’re new to this, don’t try to monitor every thought every moment. You’ll drive yourself crazy. Start with one thing. Maybe you notice you’re constantly rehashing conversations, thinking of what you should’ve said. When you catch yourself doing it, stop and pray. Do that for a month.
Or maybe you struggle with negative thoughts about yourself, that constant internal voice that says you’re a failure or nobody likes you or you’ll never get it right. Those thoughts aren’t from God. When they show up, notice them. Name them. Reject them. Ask Christ to replace them with the truth of who you are in him.
The fathers say to judge your thoughts before God. That means you’re not the final authority on whether a thought is good or bad. You bring it into the light of Christ’s commandments and see how it looks there. Does this thought lead to love? To humility? To trust in God? Or does it lead to pride, fear, division, despair?
The Long Haul
This is lifelong work. You don’t master it and move on. But over time, you get better at noticing. You catch the destructive thoughts earlier. The space between the temptation and your response gets wider. You find yourself less controlled by whatever emotion or craving or worry was running the show before.
Metropolitan Kallistos Ware and Fr. Thomas Hopko both wrote about this practice, though they often used the language of attentiveness or sobriety rather than the Greek term. The Philokalia, that collection of writings from the desert fathers and mothers, is full of teaching on nepsis. It’s not light reading, but it’s where this tradition lives in its fullest form.
For now, just start paying attention. Notice what you’re thinking. Notice where those thoughts want to take you. Stand at the door of your heart and keep watch. Pray the Jesus Prayer when the wolves show up. This is how the heart gets healed. This is how we learn to live awake instead of sleepwalking through our spiritual lives, tossed around by every passing thought and feeling. God doesn’t leave you to fight this battle alone. He gives you the prayer, the saints, the church, and his own presence. You just have to stay awake.
