"Pure religion and undefiled before our God and Father is this: to visit the fatherless and widows in their affliction, and to keep oneself unstained by the world." James 1:27
We are not of the same with the world (the system of the world) we (Christian) are of the heaven and our lives shall also dictate such.
When we romance the system of the world- sins we end up falling into such sin.
That's why the bible tells us to stay out of sin so that we won't be stained by it. Sin is not meant to be played with. We have to flee from it to remain pure.
If we are to be undefiled before God we have to stay unstained by sin.