I can't remember where I heard this from, but it is what now guides my risk per trade. "If you can't grow your account risking $1, then how are you going to grow your account risking $100." That is why after about 10 months of trading live, I figured out that my risk per trade was not adding up with what my profit target goal for the day.
I was looking to make $50 a day, but I was risking $30 per trade with a rule of trading a max of 3 trades within the day. As you can see, it makes no sense. I was willing to risk $90 within a day to make $50. Yeap, I was completely focused on the wrong thing and my math did not add up. So I changed it, I base my risk off a $5000 account as this is what BBT teaches is the minimum to trade with.
The calculation of risking 1% of $5000 a day was $51 to make 2R or $102. Since, I am willing to take 3 trades within the day, my risk per trade is now $17 per trade. This has done wonders for my equity curve and even allowed me to survive a huge draw down when I introduced a new strategy in September.
I recommend figuring out the math on what you are comfortable losing in a day and than figure out what to $risk per trade, so when everything goes wrong, you still are within your risk tolerance at the end of the day.