Business mindset is the foundation upon which we build our trading skills. This my perspective or my belief... https://www.elitetrader.com/et/threads/scaling-in-to-winning-trades.374849/page-4#post-5822389
Got it. I think it cuts a little deeper. You are going to experience losing streaks and losses on a regular basis if you trade. You need to be able to have psychology/mindset to ride those out. The fact of the matter is, once money is on the line, things get real and the discipline you thought you had, disappears. You have to have a system you trust and follow it. It sounds simple, but so many fail to do it.
Probably discipline is the key for success which as you said is a rare quality among most traders. Difficult experiences will mould a trader's discipline.
I like to scale in as price goes against me, and scale in when price moves in my direction. Context, time of day and price action dictate when I do one over the other; averaging down/up in ranging behavior, pressing in strong trending behavior. If you're going to do that you should have an idea of where you're wrong, where there is disappointment, and be able to cut for both.