I am not much of a jewelry person, but there is one piece I wear all the time:
Tiffany & Co.’s Elsa Peretti Letter “J” Pendant (product page)
J gave me this necklace soonafter we started dating, and it has adorned my neck for six years now. I never take it off — even when I’m in the shower!
Do you have a piece of jewelry you wear at all times?