I once quit trading because I couldn't control myself and struggled to engage with discipline. The various methods I tried didn't work for me personally, which meant I was stuck. After a few months, I began to realize that the fault wasn't in the method itself, but rather in my own lack of understanding of the method. This is a common problem for traders because trading methods are based on certain concepts, but they aren't able to learn them properly.
Discipline is important I agree, but sticking to the buy low sell high method is also important. Be disciplined in that and you should be able to make a good amount of money from each up-down cycle. There is very little to understand in buy low sell high method, rather what it is difficult is the ability to continue holding that low position till that high is reached and also buying multiple low positions when the market is crashing.
This crucial aspect needs to be improved, even though we know that trading isn't always profitable, as we will experience losses. However, it's not normal for someone involved in trading to always experience losses, so it's important to analyze the mistakes made so they can be corrected.
The experience in trading does help teach a naive person a thing or two about the market and how to make money from it. The average joe will leave trading but a mature joe might use the experience to come back a better trader.