A lot of traders starting out underestimate the impact that their fixed costs like spreads and commissions and even slippage have on their performance. In many cases, the criteria of selecting your instruments and timeframes might depend on these costs vs your total risk exposure. Here is a nice video about how you can overcome a lot of the issues that come along with these costs. http://www.thefxadvisor.com/posts/2009/12/optimizing-your-position-size/ Hope you enjoy it!