Holiness is not man-made, but God inspired. According to Wikipedia, holiness is the state of being holy or sacred. Holiness is being clean or pure. Merriam-Websters online definition of man-made is manufactured, created, or constructed by human beings; specifically : synthetic. One cannot make themselves holy by outward acts, self-effort, or religious duty–it cannot be manufactured or created. Outward holiness will not last–it may have the appearance of holiness, but in reality it is only a facade.
True holiness that lasts and is enduring comes from spending time with the Holy One; the perfection of holiness–our heavenly Father. We were created in His image, so the essence of who He is dwells within us. The more we are awakened to the reality of His love for us, and what He has given and sacrificed for us in His son Jesus Christ, the more we become changed from the inside out.
As His love infiltrates the deepest places of our heart, the more we crave the clean and pure things of God–His desires become ours, and our desires become His. The internal places begin to become transformed, and the outward begins to manifest His glory. Holiness is the essence of who He is and who we are to become–transformed in His glorious presence to become the holiness of God.