I disagree trade size should be based on the losses you can stomach or the dollar level that will set you over the edge and make you emotional.I agree with what Robert said. I would like to add that one needs to focus hard on the original problem. Why do people not stick to thier trading plans. Do they put them down in writing? Is it emotions getting the best of them? Perhaps its distractions in the room during trading? These are potential factors in addition to possinly being freaked out by position size.
@lescor stated it nicely here :
IMO, the number one trait that makes a good trader a great trader is the ability to let go of a mental attachment to money. It is very hard to do, and takes time. You have to be able to make rational, almost mechanical decisions based on what is the right way to execute your plan. Proper risk control relative to your account size is part of that plan, but you have to be able to think without letting where your p/l is affect you.
Everyone will have a dollar level, good and bad, for a trade or for the day, that is going to set them over the edge where they start to make poor decisions. It might be 50 dollars, it might be 50,000, but it's a curve that you try to work your way up as you grow your account.
