Danish Philosopher, Soren Kirkegaard said Purity of heart is to will one thing.
This is one of those sayings that gets stuck in your head. Think about it, purity is so often sidelined as "Don't be sexually sinful", but in fact purity is about idolatry (sexual deviance is a minor offshoot of idolatry not the whole enchilada). Jesus said, "Blessed are the pure of heart for they will see God." Mt. 5:8 Purity of heart is about living with an undivided heart, living with integrity. That no matter when anyone catches you, no matter where, no matter who you interact with you are who you are. You don't act kind, you are kind. I have been fixated on this idea for so many years.
In the November 25th meditation of Oswald Chamber's devotional My Utmost for His Highest, he says
When a person is newly born again, he seems inconsistent due to his unrelated emotions and the state of the external things or circumstances in his life. The apostle Paul had a strong and steady underlying consistency in his life. Consequently, he could let his external life change without internal distress because he was rooted and grounded in God. Most of us are not consistent spiritually because we are more concerned about being consistent externally. In the external expression of things, Paul lived in the basement, while his critics lived on the upper level. And these two levels do not begin to touch each other. But Paul’s consistency was down deep in the fundamentals. The great basis of his consistency was the agony of God in the redemption of the world, namely, the Cross of Christ.
State your beliefs to yourself again. Get back to the foundation of the Cross of Christ, doing away with any belief not based on it. In secular history the Cross is an infinitesimally small thing, but from the biblical perspective it is of more importance than all the empires of the world. If we get away from dwelling on the tragedy of God on the Cross in our preaching, our preaching produces nothing. It will not transmit the energy of God to man; it may be interesting, but it will have no power. However, when we preach the Cross, the energy of God is released. “…it pleased God through the foolishness of the message preached to save those who believe.…we preach Christ crucified…” (1 Corinthians 1:21, 23).
Purity of heart is to will one thing; Paul lived to preach Christ. As I make plans for the upcoming year, month, week, hour, I want to do it with an undivided heart. I live for Christ and I get to farm, the farm cannot be my center. If what I am doing, no matter how good it is, becomes my center I have drifted into the saddest type of idolatry, in which the gift has displaced the giver. Purity of heart is to will one thing.