You don't get it? everyone think of Sadness as a useless and negative emotion, then we learned that from Sadness comes Joy, the message here is life isn't sunshine and rainbows as kids may think, it's about how sad you get and you keep going forward that's what the writers wanted to deliver, and that's why Joy acted that way.
Regards,
To be fair, Sadness only screwed things up, and she did it to an extent that it looked like she did it on purpose. I wanted to knock her the f--- out until she became useful, since it's the only time she did anything right, and wasn't crying or anything for no reason.
@malus92 This is exactly how sadness works though.
Shout by DeletedBlockedParentSpoilers2015-06-22T00:02:38Z
Brilliant movie. I just don't give a '10' to this one because Joy was actually a bitch to Sadness on the beginning