In a nut shell, using margin to set your money management is one of the worst ways to do it because margin and the marginal leverage is just bankers and their governments protecting themselves and the brokers. Marginal leverage has nothing to do with actual trading.
The leverage that does have to do with trading is 100,000 to 1. One lot equals 100,000 units or 10,000 on a mini account, you have only those two choices, the other leverage is just how much do you want to protect your broker from you losing more than is in your account. 200 to 500 to one is good enough. Over that you are risking over drafting your account and would have to make up any difference if you should get a margin call.
Listen to togr and Adrian they have been doing this for years, use a ratio between how much you are willing to lose if everything goes wrong and the size of the trade, that is the best way to do your money management..
A lot of new traders think a low percentage of draw down is something special. I hear people brag about having no higher than 10% DD. If that is so, then by doubling their lot size using the same techniques would double their return without going over 20%.. The percentages of DD in themselves are meaningless, all we want to do is protect from a margin call. A margin call is 100% DD. Anything less is still safe so long as you are sure that the DD will not go over that amount. 50% DD is of course closer to optimal but that is a general statement because it really depends on how tight your system is.
My system is so tight, I can tell you with in a couple of dollars what my maximum draw-down would be when the price hit the highest and lowest that it has ever reached. That is my worst case so I make that amount, 50 - 60% of my balance. I don't worry about how much I am going to make, just how safe the trades are.
Hope this helps you see money management from a systemic trading point of view.
Want to also take this opportunity to say Hi to togr, always good knowing your still around my friend.
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