After compiling many trades, I checked for the longest losing streaks and how much money was lost during that losing streak. Then I take that amount of money and add it to my miniumum trading amount .
For example, if in a 25 trade losing streak and I lose $25,000 ($1000 per trade); I'll keep an extra $25,000 in my account at all times.
Incidently, this method is the one I use at the end of every quarter to decide how much money to leave in my account for the next quarterly trading period.