according to http://wiki.ffxiclopedia.org/Latent_and_Hidden_Effects this latent is triggers when your hp is red (less then 25%) and tp is less then 100%, havent tried and dont have earring so i dont know if it is true or not
The latent on this is low HP (Yellow or Red) I think its yellow. This can be really good in fights where the lag makes it impossible to time your cures with the enemies attacks. Dynamis and Besieged are good examples where this earring could be handy.