Jacen
He didn't always. He learned over time and only because Cleo had a big friggen mouth...along with us me. Galen knows everything I don't know how the moon will affect me. It's different every full moon. I could give you a list of effects we I had before but I can't guarantee they'll be the same during future moons.
I don't even know what a Sith is, so... Force User it is.