Rev 21:8

8 But for the cowardly, unbelieving, sinners, abominable, murderers, sexually immoral, sorcerers, idolaters, and all liars, their part is in the lake that burns with fire and sulfur, which is the second death.” 

cowardly – or timid, fearful. The sin of cowardice is first mentioned here. John told us that “perfect love casts out fear” (1 John 4:18). Those who are victorious, are those who do not love their own lives, even to the death (Rev 12:11, John 12:25).