Most people can understand the “holier than thou” or “so heavenly minded - no earthly good” problem. Jesus, however, chastised the Pharisees, not for their efforts to be holy and separate to God (which are good), but because they arrogantly assigned it as righteousness which resulted in judgment, disdain, contempt, or indifference for others.
There is absolutely nothing wrong (and everything right) with being a holy, separated priest and minister of the kingdom of God, who shuns and dismisses a love for all that the world and the flesh have to offer, and daily seeks the purity, peace, and purpose of the kingdom of Heaven. But holiness is about the secret intents and desires of our heart and mind that reflects our love for God and our neighbor - our character. Holiness has 1) abounding pride in being set apart to be God’s children and representatives in a fallen dark world and 2) utter humility of love that we have this treasure in earthly vessels (the flesh) with all its suffering (2 Corinthians 4:7-11) and that we can never say that we are without sin (1 John 1:8,10) [even though we can be forgiven (vs. 9)].