The most important knowledge for trading

What do you consider the most important knowledge for trading?

Know how trading works technically – how to use the broker’s platform

Know your own psychological make-up – can you follow a predetermined plan to the greatest detail without deviating in the smallest way, or do I tend to change decisions on the fly because it appears that the facts have changed?

Can I learn to keep to a plan?

Can I psychologically distance myself from my decisions and the results of my decisions?

Can I accept the outcome of a trade without letting my emotions take over?