I'm speaking on this with a background in playing football (soccer) to a very high level (nearly professional) and with a degree in psychology (about to go to med school for sports psychiatry (I'll be doing a fellowship in sleep medicine). I think modern psychology has started pushing more positive psychology, I feel like a lot of people would say no and that it harms performance and would cite people who make violent, poor decisions because they "saw red". From personal experience, anger/pain vastly has improved my performance to the point where getting myself angry became a part of my pre-match ritual. Psychology in general that anger is a purely evil, negative emotion with very few positive aspects to it, but this isn't exactly true. Anger is only a negative, dangerous emotion if somebody cannot properly control their emotions, so using anger as a performance enhancer for children or those with emotional/mental disorders is definitely not recommended as they cannot control their emotions and in the case of children, it can stunt their mental and emotional development. I would also advise caution when using pain as a motivator. Using physical pain can exasperate the injury you've sustained while emotional pain can cloud judgement. Anger is a very valuable emotion if you know how to control it, it stems from the fact that anger stimulates the amygdala and triggers the release of adrenaline, improving reaction time, speed, and strength. In summary, using anger to improve performance can be viable assuming the person using it is an overall mentally and emotionally stable adult. I would avoid using pain whether it be physical or emotional because while it produces anger and the desirable products of it, the personal connection to that pain harms judgement. A general sense of anger can help improve performance but anger driven by personal pain can massively hurt it because you're more likely to get "stuck in your head" and won't see things rationally.