Never get emotionally attached to trades.

I disagree. 

No matter how you may try to trade like a program or turn the emotion off, you are human and your emotions will always be attached to your trading. Instead of trying to ignore them, your job instead is to use your emotions as a tool. For example, learning when to recognise the signs when your trades are emotionally driven and which vary from your strategy can prove quite helpful. It is also important, which I think is in agreement with this rule, that the more systematic you make your trading – for example having a preset game plan (stops and price objectives) for every trade you make BEFORE you make it can help keep your emotions in balance so that your trading does not become emotionally driven. Again, the important thing is to learn to work with your emotions, not try to fight against them. 


For further research  I recommend  reading   "The Trading Tribe" and "Trading In The Zone"