Personally I will not be having any problem with my emotions when my trading positions are into profits zones. Only when my positions are entering into negative profits, I do lose control over my emotions like what to do next like whether to keep the positions or closing them in quick time. Moreover, these emotion control failure is pushing me toward out of my trading plan in most of the times. Probably if we plan to trade only with affordable capital which are causing no problems on losing, I believe a trader will can keep his cool mindset all the times.
I think you have some emotions that you can't control when you are in the profit zone as well, but you are too excited and happy that you can't notice. As for when you are in the negative zone, that's normal. It is normal for every trader or gambler more or less, it's also known as human nature. You should not try to fight it, as it is natural, it could do some serious harm to your mentality.
But to have consistent profits from trading, one trader must get practice to control his emotions. This is not a job of one day, it will take more time like years. When we will be practicing for years, I don't think it will be harming our mentality in any ways.
A trader should treat his profits and losses in similar manner, if it is not possible then he should take training to get practice to that. Otherwise managing emotions positively will not be possible.