How true! Emotions only affect our decision making when there is no formula on which to base our decisions. A trading plan (strategy), which I assume EVERYONE has, if followed according to its unique set of rules, eliminates emotions. If you have taken the time to test your strategy with a demo account, and IF you have gathered performance data that clearly defines what works in your strategy, and what does not, then you can have confidence in trading your strategy...even when it goes against you. For example, a win/lose ratio of 1 to 3, an average win trade of $100 and an average lose trade of $20, based on account performance over a period of time, tells you that your strategy can lose on 3 trades in a row and yet still make a profit (3 x $20 loss = $60 / 1 x $100 gain / Net $40 gain). What is there to get emotional about? Losses are stepping stones towards profit!
A strategy will comprise entry, exit, risk, and lot size rules, formulated based on past performance results. Performance data is continually collected allowing dynamic rule adjustments, i.e. stop-loss, risk factor, etc., so that a strategy remains in tune with the latest market dynamics. So you know precisely when to enter, how many lots to trade, and when to exit...no stress, no indecision, no emotional influences!