And many of these would have God will that which they themselves will, and are fretful at having to will that which He wills, and find it repugnant to accommodate their will to that of God. Hence it happens to them that oftentimes they think that that wherein they find not their own will and pleasure is not the will of God; and that, on the other hand, when they themselves find satisfaction, God is satisfied. Thus they measure God by themselves and not themselves by God, acting quite contrarily to that which He Himself taught in the Gospel, saying: That he who should lose his will for His sake, the same should gain it; and he who should desire to gain it, the same should lose it.
St. John of the Cross (2010-05-23). Dark Night of the Soul, annotated, includes active table of contents (pp. 21-22). . Kindle Edition.
He is saying sometimes we make the measure of God’s will our own pleasure and satisfaction even when we are acting in complete violation of the will of God. That is a scary thought. How do we measure our understanding of the will of God? We measure it by His Word, by the input of the godly people He has placed in our lives, by our own conscience and by prayer.