Grace does not make sin less dangerous. 

In Genesis 4:7 God warned Cain, "And if you do not do well, sin is crouching at the door; and its desire is for you, but you must master it."  In Hebrews 3:13, He cautioned, "But encourage one another day after day, as long as it is still called "Today," so that none of you will be hardened by the deceitfulness of sin." 

Sin has the power of deception. Examine yourself against the mirror of the Word. (James 1) Look upon your inner man. Be honest. If you ignore a monster in the mirror, sin's power of deception will be your master, and it may become a nightmare from which you never wake up—the worst reality of all.