Answer:
If there wasn't sadness to everyone then we wouldn't even be humans. If we had no emotions we wouldn't be humans. Sadness is what makes us humans. Yes, there is other things that makes us humans but sadness is one of the things that makes us humans.
If we didn't have sadness we would be hyper freaks.
I researched is sadness good and here's what I got
Though happiness is still desirable in many situations, there are others in which a mild sad mood confers important advantages. Findings from my own research suggest that sadness can help people details, improve attention to external educe judgmental bias, increase perseverance, and promote generosity.
the paragraph might be to hard to understand I just put that up for you if you would understand
SHORT ANSWER
Sadness is what partially makes us humans.
If your feeling depressed
know that your not alone
and get some help from your parents, teachers, friends, etc. (whoever you find more trusting)