There is nothing funky about it to tell. Max risk 1-2% of my equity per trade.... when I exceed it then I lost control of the trade (and this happens from time to time... I am only human). As a rule of thumb, I load up incrementally until my initial margin requirements get above the half of my net liquidation (sometimes I exceed this, but I shouldn't). I try to spread the risk among ESTX50, SMI, GBL, stocks, forex, and only until recently DAX. I usually reduce the positions when I am gonna go overnight. That's all. No rocket science here....
KISS risk mgmt. works best. Do you stop after a daily draw down of for example 5 %? Do you place your stops always in the market?