It is obvious that focusing solely on money (greed) or playing with scarred money is the killer in trading.
For me, it changes over time. When I started in 2008, I naively believed that it would be just a walk in the park for me. I am alright with programming skill and how difficult can it be ? I was just tired of the corporate world where I need to be extra careful not to step on someone's tail that could bite me. More than a decade later, I realise that the market is a beast that is difficult to handle. Plenty of traps. If not patient and careful, it will cost us dearly. If it's that easy, why bother getting a job.