Our God is one that is Holy and therefore if we must worship Him we have to do it with all holiness. We should not be involved in any form of unholiness. It has to be in a spiritual manner. We cannot serve God if there's impurity in our hearts.
One of the major things that we ask from God when we become born again is to purge our hearts of every form of impurities so that it can be pure and holy which is the nature it is supposed to be in order to serve Him the right way.
God delights in holiness because He is Holy. The world will live in today is full of things that is capable of causing corruption. But the Bible told us that though we are in the world we are not of the world. When the Spirit of God begins to live through us we begin to live a life of holiness and reverence to God.
Other things that people of the world do, we as Christians detach ourselves from them because it doesn't bring glory to God almighty. How we know we are living a holy life is when our day today live is structured in such a way that is glorifies God. We live our life with the consciousness that even if nobody is seeing us God is always watching us which makes us to be conscious, aware and mindful of the kind of things that we do.