The best thing for being sad is to learn something. That's the only thing that never fails. You may grow old and trembling in your anatomies, you may lie awake at night listening to the disorder od your veins, you may miss your only love. There is only one thing for it then is to learn. Learn why the world wags and what wags it. That is the only thing which the mind can never exhaust, never alienate, never be tortured by, never fear or distrust and never dream of regretting. Learning is the only thing for you.
If you know someone who is depressed, please resolve never to ask them why. Depression is not a straightforward response to a bad situation; deoression just is, like the weather.