Well, in trading, I have come to understand that one or two strategies doesn't work all the time, so you need to learn what so ever strategy that can make you win the trade so that on the stage of your trading, you might have to combine all the strategies you know in order for you to determine accurately when to enter and exit your trade.
As I am, I have more than 10 strategies to sport a good position to either go long or short but believe me, despite all of it, I don't still get it right all the time. Since last week, I have been on a short position with BTC/USDT and I took the position at $68, 800 when it broke a support level of $69k, I was in that position when price began to spike up till $73k which game me a huge lose but I didn't panic and yesterday I made about $100+ when price dropped to $67, 800.
So what am saying in essence is that, every strategy is important in trading, especially dealing with your emotions.
Emotion might not necessarily be a strategy in trading but when as a trader you don't know how to manage and handle your emotions while trading, you might not become a successful trader. It's possible that you could have all the good strategies of sporting a good entry and extit point but if other traders knows how to handle their emotions more than you and also have good strategies as you, they are going to be more successful traders than you. What I just want you to understand and also explain to your friend is that, emotions plays a very vital role in trading. I didn't see you mention it to your friend in the answer you gave to him.