Has not the LORD made them one, having a portion of the Spirit? And why one? Because He seeks godly offspring. So guard yourselves in your spirit and do not break faith with the wife of your youth. — Malachi 2:15

Malachi warns God's people: "take heed to your spirit". It's easy to focus on outward obedience while the inner man runs dry, but God looks at the heart. Guard your spirit, because the only way to keep it healthy is to stay connected to the spirit who gives life.