"External and Internal Pain"

For this post, let's say that there are two kinds of pain. Physical and emotional. Physical pain helps us in keeping ourselves safe. It's our body's way in telling us that the source of the pain is harmful, and that we should stay away from it. From a biological point of view, this is important.

On the other hand, emotional pain only eats people up. It devours people. If differentiated from its physical counterpart, it seems very useless in my opinion. Sure, just a little bit is actually useful. Fear helps us avoid potential danger, and jealousy helps some of us keep the things we have (i.e. if someone tries to steal your beloved you might opt to stop that from happening). But I'm mostly talking about sadness, anger, jealousy, etc. Basically, what we consider "negative emotions." It just doesn't make sense to me.

Personally, if there was a way to reduce the ability to feel such emotions, then I'd take it. I know people believe in the "stars can't shine without darkness" mantra, which personally I don't really subscribe to. Like mentioned in the previous paragraph, I do believe that just a little bit makes some biological sense. That's why I've only said lessen and not completely remove. But in my case, this is just too much. Sadness in particular is such a problematic feeling. I just don't understand it. How does being able to feel too much of these negative emotions help us in the physical world? I don't want sound "speciest" to you but from my understanding dogs don't have depression (although I am aware that they could feel sadness). Why can't I be more like them?

Oh, and by the way this post is titled "External and Internal Pain" because those are the terms I was originally going to use. But they I've realized that physical pain could be internal in a different sense.