When the mind is not there with the body, it's no use for the body to be at the place where the mind is not thinking.
I always say that to my fellow friends when they ask me the question "Should I go to the hospital/ should I study but I don't feel like doing it?"
My answer would be the statement above. Why bother torturing your body going to a place where your mind, heart and soul is not at, and just be there for the sake of being there? Time is so precious, we should spend it wisely, as a whole, not just as body, or as mind and so on.
That's why when the question comes to me, whether I should go to an optional extra class, or go for an extra lecture, and I don't feel like it, I would just not go. Because my mind is not set on it. Although the statement "Kiasu people always win" is the way to go in my group, I guess, I would rather lose for that moment than be lost in space, staring aimlessly at statements coming out from the lecturer's mouth and heard by my ears.
The best way for me to avoid thinking too much about the mind, body matter, I usually sleep. That's the best medicine, ever.