I don't bet to live I bet to accumulate so to me not losing the bank is THE most important thing. I try to arrange it so that it will never happen because I know if it does that will be it for me, I will stop punting and move on to something else. You seem almost as cautious as I am Duritz so I'll tell you what I do.
I get a worst drawdown figure over 10 years of bets and then add half again to that figure for safety. That is my starting bet percentage. I bet level stakes never decreasing but increasing when the bank increases. My next increase also has a bit of safety built in. Say I am betting 0.5% of the bank ($1 for every $200) I will wait until the bank grows by $250 before I increase the bet by a dollar. That way as my bank increases I also increase my safety margin. It's fairly simple and just a minor (more cautious) variation on staking systems we've all seen on here before but it makes me feel safe.

KV