Half Cup Empty or Half Cup Full???

When had my dinner today, look at the cup of green tea in front of me. I asked myself a very “out dated” question: Do I see a half cup empty of tea or half cup full of tea?

Surprise me, I didn’t know the answer. Base I on my belief: Positive attitude produces positive results, I supposed to say: "Yes, I see a half full cup of tea" BUT I didn’t this time. I think is because I am confusing tonight.