If you want to be successful then you need to apply your strategy in a consistent way and that is impossible to do if you rely on your emotions to do your trades, so the decision is simple you need to limit your emotions when you are trading because if you do not do it then the chances that you are going to become successful diminish to the point that it could be impossible to get profits otherwise.
Knowledge, strategy, practice are the things that will guide you into gaining confidence when it comes to trading and emotion is the last thing a trader want to put into their trading. The major reason why so many people tend to get emotional is because they either rushed to start making money from trading with little or no knowledge, no strategy, and no experience, and then when the reality kicked in, things started going awry.
There is no way anyone will not get emotional when you realize you are losing, market is not going the way you want, just because you actually do not have a plan. Just like in real life, it applies to trading too, because if you fail to plan, then you plan to fail.