Hey,
That is a very nice take on emotions. I also like the idea that emotions inform our mental state and I like the way you depicted the purpose of emotions. It is important to consider the embodiment of emotions and how they affect our decisions. Emotions aren't just a mental state, but an enactment of our bodies and behavior, which is ultimatley embedded within a complex social environment. Some psychologists characterize emotions on the valence and arousal scale, but I have found the approach-avoidance scales much more fascinating. This scale proposes that some emotions signify the need to avoid certain interactions (e,g, fear or disgust) whereas other emotions cause us to approach the source of that emotion (e.g. anger and happiness). As you have brilliantly pointed out, this is either good or bad. I think anger has a lot of positive benefits. Frans de Waal noticed that when primates engage in angry confrontations it is intrinsically linked to consolidatory behaviour afterwards.
I think anger can help us confront others and causes us to be truthful about issues that were bothering us. So in a way it causes us to be more truthfull. I wrote a blogpost about depression in a similar line of reasoning, tell me what you think! I resteemed this article :D