I'd say I get sad thinking that there's people going through hard times without any help. When I'm going through some shitty moment, I'm very thankful to the people who support and encourage me. It's disheartening to know that there's people who aren't lucky out there.
It'd be nice if nothing of this existed, but I'm also aware that there cannot be happiness if there is no sadness in this world. I think the best you can do yourself is spread some happiness in your own way. Maybe you can't give everybody in this planet a home and a hot meal, but you can start by helping those within reach, if you are able to.