Without a doubt, there is a glorious truth to be found in Pietism and all the religious movements akin to it. Jesus himself indeed calls us to the one thing that is necessary, namely, that we seek the kingdom of heaven above all and set aside concerns about everything else because our heavenly Father knows what we need. The life of communion with God has its own content and is not exhausted in our moral life or in the exercise of our earthly vocation.
The mystical life has its own legitimacy alongside activity; the busyness of work makes rest necessary; Sunday, though situated at the beginning of the work days, does remain next to them. In this dispensation we will never achieve the full harmony and unity that we expect in the future. Some onesideness will remain in us as persons and churches. None of us has our intellect, emotions and will, our head, heart and hand, equally governed by the Gospel.
However, in order to prevent the “spiritual” (godsdienstige), side of Christianity — that which in the good sense of the term can be called the “ascetic” side — from degenerating into an improper mysticism and monastic spirituality, it needs to be supplemented by the moral (zedelijke) — the truly human side.
Faith appears to be great, indeed, when a person renounces all and shuts himself up in isolation. But even greater, it seems to me, is the faith of the person who, while keeping the kingdom of heaven as a treasure, at the same time brings it out into the world as a leaven, certain that He who is for us is greater than he who is against us and that He is able to preserve us from evil even in the midst of the world.
— Herman Bavinck, The Catholicity of Christianity and the Church