Struggling to express negative emotions

The Emotion Coding game really brought forth my strengths and weaknesses in terms of my emotional intelligence. As far as my strengths go, I was able to recognize and guess the correct emotions being conveyed by my team members for almost all emotions except a few, which is pretty consistent with how I am in life. I am sensitive to the emotions of others and can pick up on emotions and tones right away. However I was horrible when it was my turn to act out the emotions, especially when it came to having to act the negative emotions. No one in the group could figure out what I was doing because I could not seriously read the sentences with the negative emotions. I had to read and re-read the sentences a few times. The rhymes made me laugh and distracted me. I think that in my life I do have a hard time conveying negative emotion effectively. No one really believes me when I say I am mad or upset because I think I just sort of act normal. This is something I really need to work on because in order to be an effective manager one day I will need to be able to express disappointment and frustration at the appropriate time and not act cheerful and act like I don’t really care. So I was able to identify that I am pretty good at recognizing and understand emotions in others but I need to work on expressing my own emotions especially negative ones.