[Gorthaur the Cruel]

It was at that time that she received Nenya, the White Ring, from Celebrimbor, and by its power the realm of Lórinand was strengthened and made beautiful; but its power upon her was great also and unforseen, for it increased her latent desire for the Sea and for return into the West, so that her joy in Middle-earth was diminished. --Unfinished Tales, "THG&C"

I don't understand why this had a side-effect on her. Can any experts try to give theories please.