I would like to add one more thing to what italianfx said.
Usually you shouldnt risk more than 2-3 % of your account is first of all just a thumbrule it depends totally on your mentality if you are willing to risk up to 5%. But you have to be able to deal with bigger drawdowns!
Now what is also a very important factor in this is simply the accuracy of the system and seriously when linuxtroll has a 99% accuracy i dont think he would mind risking 10% of his account on a trade.
Usually you shouldnt risk more than 2-3 % of your account is first of all just a thumbrule it depends totally on your mentality if you are willing to risk up to 5%. But you have to be able to deal with bigger drawdowns!
Now what is also a very important factor in this is simply the accuracy of the system and seriously when linuxtroll has a 99% accuracy i dont think he would mind risking 10% of his account on a trade.