In my opinion, there is nothing wrong with being a bit angry or jealous sometimes.
You shouldn’t throw your rage at the people around you or let your actions be driven by anger alone. But there are a lot of things one can very justly be angry about. I would even argue that some things one should feel angry about. Like when someone is mistreated.
Denying yourself negative emotions is not entirely healthy in my opinion, it’s more about the way you act on them (or don’t act on them).
I think I remember some years ago a zoo fed a dead giraffe to the lions and people went absolutely insane about it. I’m not sure about the details anymore, they might have killed it because there wasn’t enough room in the zoo for it? Either way I didn’t get it, what do they think the lions are fed any other day? Animals that weren’t killed explicitly to become food? Some cows that couldn’t bear existence on this world anymore and offered themselves as lion food? Where is the difference?