When you get mad at an rp, I find that what used to help me when I was new was that I needed to take a step back, shower or make my bed or whatever to kinda let it sit. That way I didn't react out of anger to disgrace the character I played. Unless the character would be angry, then I utilized the crap out of it. 
NEVER go against what your character would do unless it is a pinnacle of change, the showing of a hidden emotion (within reason) or for someone other than themselves. 

When you make a character, you have become a small god, in your own way. You have made a 'walking,' 'talking' 'breathing' individual who has a past and it has carved them. The same goes for writing your own personal works, rather than just Rping, which I have done before. As 'god' you are the observer. If you get angry, who the FUCK are you to take it out on your creation? You are taking away the free will that gives your creature, your creation the beauty that is. The mind of it is different than your own, and therefore fascinating. 
I have made characters older than I, Younger than I, and the same age. Many wiser, some naive and innocent, some arrogant and inconsiderate. Some are evil, some are good, some are in situations I will never be in no matter how bad I may desire the life I have chosen for them to live... And every single one of them has taught me a different lesson about life.

I am unique..... but I am not who I create. 

And if you ask me that's pretty fucking beautiful.