It is often said that sadness inspires artists. For my part, I like it when we transform sad or negative things into art; it's finally transforming all those things that harm us into beautiful things that revive us.
Sadness is useful in itself, and you have to know how to take it on the right side, why it happens, to be able to improve your life.
What you do with it in your drawings is probably one of the best ways. Stay positive, and don't stop creating! :)