A typical example would be a trader who likes to trade just one setup that may only occasionally occur in ES, so he scours many many markets looking for his setup. These are the guys who really work for a living and probably have a better chance of success. I traded nothing but ES for many years but had to take some huge risks that I would not take now. I would certainly not call what I was doing sensible. The only thing that saved me was I had to withdraw money every month to pay bills and that kept me from adding size to my stupidity when things were seemingly going well.
Let's just put it this way, it ended with one big "Hail Mary" which somehow miraculously got caught in the end zone by a guy on my team, and that's when I quit, because after beating my head against the wall everyday trading that ES if nothing else, I had learned the difference between luck and skill.
I am overwhelmed by the amount of advice I got. Thanks a lot everyone. Will practice more and get my hands some more reading material. Once I feel comfortable enough with the volatility of ES and I have a good method of trading it, I will start. For now, I'll stick to 2x and 3x ETFs.