Feeling like I have nothing left to give to the world

Time to time, after a long day at work, I would lay down on my bed and stare at my ceiling blankly. My energy drained, my mind filled with nothing but emptiness. I felt like throughout the day, I have offered others everything there was to me. Even if I tried, I couldn’t give out anymore, because there was already nothing left for me to give . Why do I feel empty? I…