The spell only expires when reaching 0 HP, which means the player can rest at bonfires and even unequip the miracle, freeing up two spell slots while still being under its effects. The miracle will, however, be removed if the player travels to another area (by using bonfires, Homeward or a Homeward Bone) or if exiting the game.
Tears of Denial will also prevent death by Curse. However, curse build-up will not be cured, meaning that this effect has no practical application against Basilisks and Clawed Curses.
Weapons/spells that doe rapid strikes, and damage over time effects can render the spell null in pvp. As the spell activates the first moment you are rendered to 0 hp, and any following attacks can finish the player.