Teach your kid to think practically instead of emotionally
Your child is naturally emotional at this age. So you need to develop his practical thinking and common sense. Instruct him carefully and gently on how to deal with a situation not just emotionally, but pragmatically too.
When your kid faces any small problem, take note of how he reacts. If he tends to get very upset or irritated, say nothing at that time, but have a quiet discussion with him once he is calm. Ask him why he got so worked up, and then explain to him how this is not productive. Together, look at the problem once more, and let him see how being calm helps him to think more clearly and resolve the issue effectively.
Discuss, not debate in an assertive tone. You need to teach your kid to see a problem from a logical and unemotional perspective. If he is getting worked up, remind him of your previous discussions and advise him to be calm. Frequent gentle reminders will help him.